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	$230.50	10.433%	$254.5481	$254.55	$254.55	$254.50
Purchase #2	$21.47	4.454%	$22.4263	$22.43	$22.45	$22.40
Purchase #3	$94.37	11.202%	$104.9413	$104.94	$104.95	$104.90
Purchase #4	$17.49	5.618%	$18.4726	$18.47	$18.45	$18.50
Purchase #5	$50.26	12.497%	$56.541	$56.54	$56.55	$56.50
Purchase #6	$63.41	12.780%	$71.5138	$71.51	$71.50	$71.50
Purchase #7	$148.32	12.286%	$166.5426	$166.54	$166.55	$166.50
7 purchase totals =	$625.82		$694.9857	$694.98	$695.00	$694.80