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	$113.25	12.559%	$127.4731	$127.47	$127.45	$127.50
Purchase #2	$72.95	9.778%	$80.0831	$80.08	$80.10	$80.10
Purchase #3	$228.70	5.556%	$241.4066	$241.41	$241.40	$241.40
Purchase #4	$209.29	10.633%	$231.5438	$231.54	$231.55	$231.50
Purchase #5	$41.56	3.677%	$43.0882	$43.09	$43.10	$43.10
Purchase #6	$40.93	13.655%	$46.519	$46.52	$46.50	$46.50
Purchase #7	$172.91	11.746%	$193.22	$193.22	$193.20	$193.20
7 purchase totals =	$879.59		$963.3338	$963.33	$963.30	$963.30