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	$51.34	3.846%	$53.3145	$53.31	$53.30	$53.30
Purchase #2	$92.62	5.671%	$97.8725	$97.87	$97.85	$97.90
Purchase #3	$129.76	12.610%	$146.1227	$146.12	$146.10	$146.10
Purchase #4	$137.89	13.388%	$156.3507	$156.35	$156.35	$156.40
Purchase #5	$210.92	12.869%	$238.0633	$238.06	$238.05	$238.10
Purchase #6	$170.88	8.812%	$185.9379	$185.94	$185.95	$185.90
Purchase #7	$147.74	5.569%	$155.9676	$155.97	$155.95	$156.00
7 purchase totals =	$941.15		$1,033.6292	$1,033.62	$1,033.55	$1,033.70