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	$124.52	13.760%	$141.654	$141.65	$141.65	$141.70
Purchase #2	$18.82	12.552%	$21.1823	$21.18	$21.20	$21.20
Purchase #3	$197.94	3.817%	$205.4954	$205.50	$205.50	$205.50
Purchase #4	$56.50	4.710%	$59.1612	$59.16	$59.15	$59.20
Purchase #5	$187.93	9.298%	$205.4037	$205.40	$205.40	$205.40
Purchase #6	$189.53	11.459%	$211.2482	$211.25	$211.25	$211.20
Purchase #7	$90.71	13.191%	$102.6756	$102.68	$102.70	$102.70
7 purchase totals =	$865.95		$946.8204	$946.82	$946.85	$946.90