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	$71.75	9.790%	$78.7743	$78.77	$78.75	$78.80
Purchase #2	$199.77	10.864%	$221.473	$221.47	$221.45	$221.50
Purchase #3	$54.69	3.300%	$56.4948	$56.49	$56.50	$56.50
Purchase #4	$195.47	13.641%	$222.1341	$222.13	$222.15	$222.10
Purchase #5	$60.84	12.855%	$68.661	$68.66	$68.65	$68.70
Purchase #6	$149.79	7.120%	$160.455	$160.46	$160.45	$160.50
Purchase #7	$69.44	11.686%	$77.5548	$77.55	$77.55	$77.60
7 purchase totals =	$801.75		$885.5470	$885.53	$885.50	$885.70