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	$178.31	12.540%	$200.6701	$200.67	$200.65	$200.70
Purchase #2	$89.33	5.554%	$94.2914	$94.29	$94.30	$94.30
Purchase #3	$103.53	11.226%	$115.1523	$115.15	$115.15	$115.20
Purchase #4	$245.83	12.125%	$275.6369	$275.64	$275.65	$275.60
Purchase #5	$133.64	13.487%	$151.664	$151.66	$151.65	$151.70
Purchase #6	$188.71	13.618%	$214.4085	$214.41	$214.40	$214.40
Purchase #7	$71.43	11.572%	$79.6959	$79.70	$79.70	$79.70
7 purchase totals =	$1,010.78		$1,131.5191	$1,131.52	$1,131.50	$1,131.60