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	$229.54	9.459%	$251.2522	$251.25	$251.25	$251.30
Purchase #2	$182.34	13.316%	$206.6204	$206.62	$206.60	$206.60
Purchase #3	$93.31	12.612%	$105.0783	$105.08	$105.10	$105.10
Purchase #4	$74.81	12.189%	$83.9286	$83.93	$83.95	$83.90
Purchase #5	$157.26	3.302%	$162.4527	$162.45	$162.45	$162.50
Purchase #6	$95.91	7.654%	$103.251	$103.25	$103.25	$103.30
Purchase #7	$160.35	3.434%	$165.8564	$165.86	$165.85	$165.90
7 purchase totals =	$993.52		$1,078.4396	$1,078.44	$1,078.45	$1,078.60