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	$226.81	6.774%	$242.1741	$242.17	$242.15	$242.20
Purchase #2	$240.61	11.186%	$267.5246	$267.52	$267.50	$267.50
Purchase #3	$162.63	3.861%	$168.9091	$168.91	$168.90	$168.90
Purchase #4	$26.29	8.728%	$28.5846	$28.58	$28.60	$28.60
Purchase #5	$50.54	5.488%	$53.3136	$53.31	$53.30	$53.30
Purchase #6	$225.33	13.514%	$255.7811	$255.78	$255.80	$255.80
Purchase #7	$43.94	9.831%	$48.2597	$48.26	$48.25	$48.30
7 purchase totals =	$976.15		$1,064.5468	$1,064.53	$1,064.50	$1,064.60