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	$70.43	10.117%	$77.5554	$77.56	$77.55	$77.60
Purchase #2	$151.42	13.727%	$172.2054	$172.21	$172.20	$172.20
Purchase #3	$38.89	4.792%	$40.7536	$40.75	$40.75	$40.80
Purchase #4	$5.82	5.133%	$6.1187	$6.12	$6.10	$6.10
Purchase #5	$145.67	9.452%	$159.4387	$159.44	$159.45	$159.40
Purchase #6	$243.73	10.690%	$269.7847	$269.78	$269.80	$269.80
Purchase #7	$250.32	13.635%	$284.4511	$284.45	$284.45	$284.50
7 purchase totals =	$906.28		$1,010.3076	$1,010.31	$1,010.30	$1,010.40