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	$236.33	5.557%	$249.4629	$249.46	$249.45	$249.50
Purchase #2	$144.47	5.555%	$152.4953	$152.50	$152.50	$152.50
Purchase #3	$215.56	9.736%	$236.5469	$236.55	$236.55	$236.50
Purchase #4	$220.49	12.186%	$247.3589	$247.36	$247.35	$247.40
Purchase #5	$144.56	9.457%	$158.231	$158.23	$158.25	$158.20
Purchase #6	$95.88	10.151%	$105.6128	$105.61	$105.60	$105.60
Purchase #7	$176.58	8.359%	$191.3403	$191.34	$191.35	$191.30
7 purchase totals =	$1,233.87		$1,341.0481	$1,341.05	$1,341.05	$1,341.00