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	$89.86	10.645%	$99.4256	$99.43	$99.45	$99.40
Purchase #2	$76.37	12.700%	$86.069	$86.07	$86.05	$86.10
Purchase #3	$135.75	4.679%	$142.1017	$142.10	$142.10	$142.10
Purchase #4	$151.64	9.207%	$165.6015	$165.60	$165.60	$165.60
Purchase #5	$198.85	12.561%	$223.8275	$223.83	$223.85	$223.80
Purchase #6	$224.62	11.516%	$250.4872	$250.49	$250.50	$250.50
Purchase #7	$50.31	9.717%	$55.1986	$55.20	$55.20	$55.20
7 purchase totals =	$927.40		$1,022.7111	$1,022.72	$1,022.75	$1,022.70