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	$235.74	13.553%	$267.6898	$267.69	$267.70	$267.70
Purchase #2	$169.65	9.567%	$185.8804	$185.88	$185.90	$185.90
Purchase #3	$38.25	9.494%	$41.8815	$41.88	$41.90	$41.90
Purchase #4	$198.48	6.649%	$211.6769	$211.68	$211.70	$211.70
Purchase #5	$150.73	11.371%	$167.8695	$167.87	$167.85	$167.90
Purchase #6	$35.71	4.496%	$37.3155	$37.32	$37.30	$37.30
Purchase #7	$140.79	7.261%	$151.0128	$151.01	$151.00	$151.00
7 purchase totals =	$969.35		$1,063.3264	$1,063.33	$1,063.35	$1,063.40