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	$63.96	11.233%	$71.1446	$71.14	$71.15	$71.10
Purchase #2	$182.39	6.445%	$194.145	$194.15	$194.15	$194.10
Purchase #3	$22.76	9.621%	$24.9497	$24.95	$24.95	$24.90
Purchase #4	$210.30	8.600%	$228.3858	$228.39	$228.40	$228.40
Purchase #5	$37.90	4.299%	$39.5293	$39.53	$39.55	$39.50
Purchase #6	$56.76	9.809%	$62.3276	$62.33	$62.35	$62.30
Purchase #7	$59.66	11.635%	$66.6014	$66.60	$66.60	$66.60
7 purchase totals =	$633.73		$687.0834	$687.09	$687.15	$686.90