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	$143.29	8.791%	$155.8866	$155.89	$155.90	$155.90
Purchase #2	$53.28	7.363%	$57.203	$57.20	$57.20	$57.20
Purchase #3	$223.29	9.467%	$244.4289	$244.43	$244.45	$244.40
Purchase #4	$49.94	9.371%	$54.6199	$54.62	$54.60	$54.60
Purchase #5	$179.63	5.662%	$189.8007	$189.80	$189.80	$189.80
Purchase #6	$196.40	4.759%	$205.7467	$205.75	$205.75	$205.70
Purchase #7	$58.70	4.831%	$61.5358	$61.54	$61.55	$61.50
7 purchase totals =	$904.53		$969.2216	$969.23	$969.25	$969.10