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	$86.54	3.731%	$89.7688	$89.77	$89.75	$89.80
Purchase #2	$54.69	8.793%	$59.4989	$59.50	$59.50	$59.50
Purchase #3	$42.84	12.463%	$48.1791	$48.18	$48.20	$48.20
Purchase #4	$39.56	11.791%	$44.2245	$44.22	$44.20	$44.20
Purchase #5	$188.52	5.125%	$198.1817	$198.18	$198.20	$198.20
Purchase #6	$230.32	7.183%	$246.8639	$246.86	$246.85	$246.90
Purchase #7	$38.44	4.449%	$40.1502	$40.15	$40.15	$40.20
7 purchase totals =	$680.91		$726.8671	$726.86	$726.85	$727.00