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	$95.89	13.530%	$108.8639	$108.86	$108.85	$108.90
Purchase #2	$56.82	9.869%	$62.4276	$62.43	$62.45	$62.40
Purchase #3	$118.56	4.659%	$124.0837	$124.08	$124.10	$124.10
Purchase #4	$93.33	5.125%	$98.1132	$98.11	$98.10	$98.10
Purchase #5	$95.90	9.346%	$104.8628	$104.86	$104.85	$104.90
Purchase #6	$83.82	7.257%	$89.9028	$89.90	$89.90	$89.90
Purchase #7	$150.79	6.717%	$160.9186	$160.92	$160.90	$160.90
7 purchase totals =	$695.11		$749.1726	$749.16	$749.15	$749.20