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	$136.37	9.102%	$148.7824	$148.78	$148.80	$148.80
Purchase #2	$220.52	12.242%	$247.5161	$247.52	$247.50	$247.50
Purchase #3	$171.47	3.844%	$178.0613	$178.06	$178.05	$178.10
Purchase #4	$176.59	8.224%	$191.1128	$191.11	$191.10	$191.10
Purchase #5	$34.52	9.684%	$37.8629	$37.86	$37.85	$37.90
Purchase #6	$121.25	5.153%	$127.498	$127.50	$127.50	$127.50
Purchase #7	$221.98	13.480%	$251.9029	$251.90	$251.90	$251.90
7 purchase totals =	$1,082.70		$1,182.7364	$1,182.73	$1,182.70	$1,182.80