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	$151.46	8.501%	$164.3356	$164.34	$164.35	$164.30
Purchase #2	$236.33	5.850%	$250.1553	$250.16	$250.15	$250.20
Purchase #3	$190.52	11.520%	$212.4679	$212.47	$212.45	$212.50
Purchase #4	$149.44	4.369%	$155.969	$155.97	$155.95	$156.00
Purchase #5	$244.34	7.861%	$263.5476	$263.55	$263.55	$263.50
Purchase #6	$58.25	12.511%	$65.5377	$65.54	$65.55	$65.50
Purchase #7	$111.51	4.855%	$116.9238	$116.92	$116.90	$116.90
7 purchase totals =	$1,141.85		$1,228.9369	$1,228.95	$1,228.90	$1,228.90