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	$75.41	3.727%	$78.2205	$78.22	$78.20	$78.20
Purchase #2	$67.44	3.259%	$69.6379	$69.64	$69.65	$69.60
Purchase #3	$89.69	11.652%	$100.1407	$100.14	$100.15	$100.10
Purchase #4	$34.96	5.171%	$36.7678	$36.77	$36.75	$36.80
Purchase #5	$223.37	13.481%	$253.4825	$253.48	$253.50	$253.50
Purchase #6	$239.51	3.753%	$248.4988	$248.50	$248.50	$248.50
Purchase #7	$152.85	3.785%	$158.6354	$158.64	$158.65	$158.60
7 purchase totals =	$883.23		$945.3836	$945.39	$945.40	$945.30