Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.60	5.272%	$168.0141	$168.01	$168.00	$168.00
Purchase #2	$167.68	7.318%	$179.9508	$179.95	$179.95	$180.00
Purchase #3	$195.56	13.718%	$222.3869	$222.39	$222.40	$222.40
Purchase #4	$157.40	6.253%	$167.2422	$167.24	$167.25	$167.20
Purchase #5	$216.27	13.243%	$244.9106	$244.91	$244.90	$244.90
Purchase #6	$110.79	12.752%	$124.9179	$124.92	$124.90	$124.90
Purchase #7	$154.76	5.196%	$162.8013	$162.80	$162.80	$162.80
7 purchase totals =	$1,162.06		$1,270.2238	$1,270.22	$1,270.20	$1,270.20