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	$161.62	11.302%	$179.8863	$179.89	$179.90	$179.90
Purchase #2	$147.61	13.841%	$168.0407	$168.04	$168.05	$168.00
Purchase #3	$248.58	5.469%	$262.1748	$262.17	$262.15	$262.20
Purchase #4	$204.90	9.323%	$224.0028	$224.00	$224.00	$224.00
Purchase #5	$139.65	3.505%	$144.5447	$144.54	$144.55	$144.50
Purchase #6	$38.59	13.815%	$43.9212	$43.92	$43.90	$43.90
Purchase #7	$91.69	10.180%	$101.024	$101.02	$101.00	$101.00
7 purchase totals =	$1,032.64		$1,123.5945	$1,123.58	$1,123.55	$1,123.50