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	$232.85	13.555%	$264.4128	$264.41	$264.40	$264.40
Purchase #2	$215.53	4.599%	$225.4422	$225.44	$225.45	$225.40
Purchase #3	$158.37	4.290%	$165.1641	$165.16	$165.15	$165.20
Purchase #4	$51.26	10.401%	$56.5916	$56.59	$56.60	$56.60
Purchase #5	$243.60	12.673%	$274.4714	$274.47	$274.45	$274.50
Purchase #6	$239.56	10.225%	$264.055	$264.06	$264.05	$264.10
Purchase #7	$216.74	12.293%	$243.3838	$243.38	$243.40	$243.40
7 purchase totals =	$1,357.91		$1,493.5209	$1,493.51	$1,493.50	$1,493.60