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	$60.59	9.330%	$66.243	$66.24	$66.25	$66.20
Purchase #2	$143.36	11.843%	$160.3381	$160.34	$160.35	$160.30
Purchase #3	$38.39	11.807%	$42.9227	$42.92	$42.90	$42.90
Purchase #4	$191.28	6.191%	$203.1221	$203.12	$203.10	$203.10
Purchase #5	$227.44	4.717%	$238.1683	$238.17	$238.15	$238.20
Purchase #6	$108.65	7.789%	$117.1127	$117.11	$117.10	$117.10
Purchase #7	$211.34	3.446%	$218.6228	$218.62	$218.60	$218.60
7 purchase totals =	$981.05		$1,046.5297	$1,046.52	$1,046.45	$1,046.40