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	$168.94	11.588%	$188.5168	$188.52	$188.50	$188.50
Purchase #2	$247.81	13.566%	$281.4279	$281.43	$281.45	$281.40
Purchase #3	$43.78	13.315%	$49.6093	$49.61	$49.60	$49.60
Purchase #4	$37.49	9.356%	$40.9976	$41.00	$41.00	$41.00
Purchase #5	$191.69	7.274%	$205.6335	$205.63	$205.65	$205.60
Purchase #6	$204.86	9.180%	$223.6661	$223.67	$223.65	$223.70
Purchase #7	$183.86	8.581%	$199.637	$199.64	$199.65	$199.60
7 purchase totals =	$1,078.43		$1,189.4882	$1,189.50	$1,189.50	$1,189.40