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	$68.99	11.694%	$77.0577	$77.06	$77.05	$77.10
Purchase #2	$213.73	11.627%	$238.5804	$238.58	$238.60	$238.60
Purchase #3	$185.95	9.228%	$203.1095	$203.11	$203.10	$203.10
Purchase #4	$37.31	8.394%	$40.4418	$40.44	$40.45	$40.40
Purchase #5	$37.28	8.384%	$40.4056	$40.41	$40.40	$40.40
Purchase #6	$237.66	11.425%	$264.8127	$264.81	$264.80	$264.80
Purchase #7	$81.53	10.171%	$89.8224	$89.82	$89.80	$89.80
7 purchase totals =	$862.45		$954.2301	$954.23	$954.20	$954.20