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	$61.26	3.536%	$63.4262	$63.43	$63.45	$63.40
Purchase #2	$97.37	3.260%	$100.5443	$100.54	$100.55	$100.50
Purchase #3	$28.34	7.807%	$30.5525	$30.55	$30.55	$30.60
Purchase #4	$109.27	10.309%	$120.5346	$120.53	$120.55	$120.50
Purchase #5	$216.43	4.149%	$225.4097	$225.41	$225.40	$225.40
Purchase #6	$147.59	12.585%	$166.1642	$166.16	$166.15	$166.20
Purchase #7	$59.28	5.855%	$62.7508	$62.75	$62.75	$62.80
7 purchase totals =	$719.54		$769.3823	$769.37	$769.40	$769.40