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	$139.29	8.808%	$151.5587	$151.56	$151.55	$151.60
Purchase #2	$235.82	9.132%	$257.3551	$257.36	$257.35	$257.40
Purchase #3	$45.36	11.264%	$50.4694	$50.47	$50.45	$50.50
Purchase #4	$113.30	7.819%	$122.1589	$122.16	$122.15	$122.20
Purchase #5	$86.53	10.304%	$95.4461	$95.45	$95.45	$95.40
Purchase #6	$170.62	4.580%	$178.4344	$178.43	$178.45	$178.40
Purchase #7	$142.72	6.439%	$151.9097	$151.91	$151.90	$151.90
7 purchase totals =	$933.64		$1,007.3323	$1,007.34	$1,007.30	$1,007.40