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	$133.90	10.233%	$147.602	$147.60	$147.60	$147.60
Purchase #2	$110.58	12.707%	$124.6314	$124.63	$124.65	$124.60
Purchase #3	$149.45	13.450%	$169.551	$169.55	$169.55	$169.60
Purchase #4	$180.79	5.617%	$190.945	$190.95	$190.95	$190.90
Purchase #5	$72.43	8.695%	$78.7278	$78.73	$78.75	$78.70
Purchase #6	$149.78	11.679%	$167.2728	$167.27	$167.25	$167.30
Purchase #7	$151.66	11.844%	$169.6226	$169.62	$169.60	$169.60
7 purchase totals =	$948.59		$1,048.3526	$1,048.35	$1,048.35	$1,048.30