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	$57.72	7.830%	$62.2395	$62.24	$62.25	$62.20
Purchase #2	$32.78	13.209%	$37.1099	$37.11	$37.10	$37.10
Purchase #3	$62.31	6.523%	$66.3745	$66.37	$66.35	$66.40
Purchase #4	$238.56	9.284%	$260.7079	$260.71	$260.70	$260.70
Purchase #5	$96.83	12.758%	$109.1836	$109.18	$109.20	$109.20
Purchase #6	$131.60	11.557%	$146.809	$146.81	$146.80	$146.80
Purchase #7	$63.33	11.688%	$70.732	$70.73	$70.75	$70.70
7 purchase totals =	$683.13		$753.1564	$753.15	$753.15	$753.10