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	$95.85	8.434%	$103.934	$103.93	$103.95	$103.90
Purchase #2	$38.30	10.639%	$42.3747	$42.37	$42.35	$42.40
Purchase #3	$196.89	11.777%	$220.0777	$220.08	$220.10	$220.10
Purchase #4	$159.76	13.184%	$180.8228	$180.82	$180.80	$180.80
Purchase #5	$209.60	5.818%	$221.7945	$221.79	$221.80	$221.80
Purchase #6	$54.31	10.422%	$59.9702	$59.97	$59.95	$60.00
Purchase #7	$84.44	3.675%	$87.5432	$87.54	$87.55	$87.50
7 purchase totals =	$839.15		$916.5171	$916.50	$916.50	$916.50