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	$123.95	5.273%	$130.4859	$130.49	$130.50	$130.50
Purchase #2	$26.79	5.430%	$28.2447	$28.24	$28.25	$28.20
Purchase #3	$197.59	13.122%	$223.5178	$223.52	$223.50	$223.50
Purchase #4	$47.81	5.289%	$50.3387	$50.34	$50.35	$50.30
Purchase #5	$67.63	5.772%	$71.5336	$71.53	$71.55	$71.50
Purchase #6	$201.33	4.857%	$211.1086	$211.11	$211.10	$211.10
Purchase #7	$112.33	5.573%	$118.5902	$118.59	$118.60	$118.60
7 purchase totals =	$777.43		$833.8195	$833.82	$833.85	$833.70