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	$58.52	6.146%	$62.1166	$62.12	$62.10	$62.10
Purchase #2	$169.92	12.537%	$191.2229	$191.22	$191.20	$191.20
Purchase #3	$70.67	7.460%	$75.942	$75.94	$75.95	$75.90
Purchase #4	$128.59	13.580%	$146.0525	$146.05	$146.05	$146.10
Purchase #5	$231.91	9.454%	$253.8348	$253.83	$253.85	$253.80
Purchase #6	$119.70	9.487%	$131.0559	$131.06	$131.05	$131.10
Purchase #7	$191.59	4.818%	$200.8208	$200.82	$200.80	$200.80
7 purchase totals =	$970.90		$1,061.0455	$1,061.04	$1,061.00	$1,061.00