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	$46.30	5.650%	$48.916	$48.92	$48.90	$48.90
Purchase #2	$16.85	9.333%	$18.4226	$18.42	$18.40	$18.40
Purchase #3	$145.33	6.110%	$154.2097	$154.21	$154.20	$154.20
Purchase #4	$101.71	9.848%	$111.7264	$111.73	$111.75	$111.70
Purchase #5	$104.60	7.111%	$112.0381	$112.04	$112.05	$112.00
Purchase #6	$239.86	12.371%	$269.5331	$269.53	$269.55	$269.50
Purchase #7	$152.62	5.696%	$161.3132	$161.31	$161.30	$161.30
7 purchase totals =	$807.27		$876.1591	$876.16	$876.15	$876.00