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	$145.70	13.446%	$165.2908	$165.29	$165.30	$165.30
Purchase #2	$189.63	8.486%	$205.722	$205.72	$205.70	$205.70
Purchase #3	$242.97	5.406%	$256.105	$256.11	$256.10	$256.10
Purchase #4	$153.74	5.700%	$162.5032	$162.50	$162.50	$162.50
Purchase #5	$57.83	5.287%	$60.8875	$60.89	$60.90	$60.90
Purchase #6	$219.86	11.629%	$245.4275	$245.43	$245.45	$245.40
Purchase #7	$8.29	7.244%	$8.8905	$8.89	$8.90	$8.90
7 purchase totals =	$1,018.02		$1,104.8265	$1,104.83	$1,104.85	$1,104.80