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	$224.28	13.262%	$254.024	$254.02	$254.00	$254.00
Purchase #2	$93.38	6.464%	$99.4161	$99.42	$99.40	$99.40
Purchase #3	$53.57	13.639%	$60.8764	$60.88	$60.90	$60.90
Purchase #4	$145.53	10.397%	$160.6608	$160.66	$160.65	$160.70
Purchase #5	$147.62	6.834%	$157.7084	$157.71	$157.70	$157.70
Purchase #6	$137.90	7.714%	$148.5376	$148.54	$148.55	$148.50
Purchase #7	$166.77	11.494%	$185.9385	$185.94	$185.95	$185.90
7 purchase totals =	$969.05		$1,067.1618	$1,067.17	$1,067.15	$1,067.10