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	$162.48	6.232%	$172.6058	$172.61	$172.60	$172.60
Purchase #2	$155.60	9.520%	$170.4131	$170.41	$170.40	$170.40
Purchase #3	$96.72	3.104%	$99.7222	$99.72	$99.70	$99.70
Purchase #4	$178.60	12.115%	$200.2374	$200.24	$200.25	$200.20
Purchase #5	$156.66	9.332%	$171.2795	$171.28	$171.30	$171.30
Purchase #6	$231.77	5.411%	$244.3111	$244.31	$244.30	$244.30
Purchase #7	$39.34	8.771%	$42.7905	$42.79	$42.80	$42.80
7 purchase totals =	$1,021.17		$1,101.3596	$1,101.36	$1,101.35	$1,101.30