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	$73.74	4.148%	$76.7987	$76.80	$76.80	$76.80
Purchase #2	$57.92	5.793%	$61.2753	$61.28	$61.30	$61.30
Purchase #3	$247.89	5.237%	$260.872	$260.87	$260.85	$260.90
Purchase #4	$57.73	3.218%	$59.5878	$59.59	$59.60	$59.60
Purchase #5	$84.79	11.168%	$94.2593	$94.26	$94.25	$94.30
Purchase #6	$204.74	12.287%	$229.8964	$229.90	$229.90	$229.90
Purchase #7	$103.71	7.713%	$111.7092	$111.71	$111.70	$111.70
7 purchase totals =	$830.52		$894.3987	$894.41	$894.40	$894.50