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	$42.85	9.435%	$46.8929	$46.89	$46.90	$46.90
Purchase #2	$55.29	11.354%	$61.5676	$61.57	$61.55	$61.60
Purchase #3	$186.86	10.854%	$207.1418	$207.14	$207.15	$207.10
Purchase #4	$93.25	12.574%	$104.9753	$104.98	$105.00	$105.00
Purchase #5	$231.50	9.303%	$253.0364	$253.04	$253.05	$253.00
Purchase #6	$217.25	4.527%	$227.0849	$227.08	$227.10	$227.10
Purchase #7	$111.33	6.717%	$118.808	$118.81	$118.80	$118.80
7 purchase totals =	$938.33		$1,019.5069	$1,019.51	$1,019.55	$1,019.50