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	$165.51	12.113%	$185.5582	$185.56	$185.55	$185.60
Purchase #2	$100.56	12.752%	$113.3834	$113.38	$113.40	$113.40
Purchase #3	$185.71	13.874%	$211.4754	$211.48	$211.50	$211.50
Purchase #4	$105.40	3.142%	$108.7117	$108.71	$108.70	$108.70
Purchase #5	$201.63	11.294%	$224.4021	$224.40	$224.40	$224.40
Purchase #6	$152.75	8.163%	$165.219	$165.22	$165.20	$165.20
Purchase #7	$119.76	4.851%	$125.5696	$125.57	$125.55	$125.60
7 purchase totals =	$1,031.32		$1,134.3194	$1,134.32	$1,134.30	$1,134.40