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	$241.45	9.601%	$264.6316	$264.63	$264.65	$264.60
Purchase #2	$33.58	10.685%	$37.168	$37.17	$37.15	$37.20
Purchase #3	$182.52	6.729%	$194.8018	$194.80	$194.80	$194.80
Purchase #4	$87.70	13.854%	$99.85	$99.85	$99.85	$99.90
Purchase #5	$115.30	8.304%	$124.8745	$124.87	$124.85	$124.90
Purchase #6	$126.91	12.331%	$142.5593	$142.56	$142.55	$142.60
Purchase #7	$246.58	12.208%	$276.6825	$276.68	$276.70	$276.70
7 purchase totals =	$1,034.04		$1,140.5677	$1,140.56	$1,140.55	$1,140.70