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	$189.70	13.287%	$214.9054	$214.91	$214.90	$214.90
Purchase #2	$191.67	12.847%	$216.2938	$216.29	$216.30	$216.30
Purchase #3	$162.37	8.486%	$176.1487	$176.15	$176.15	$176.10
Purchase #4	$244.36	7.183%	$261.9124	$261.91	$261.90	$261.90
Purchase #5	$90.96	6.329%	$96.7169	$96.72	$96.70	$96.70
Purchase #6	$234.46	9.566%	$256.8884	$256.89	$256.90	$256.90
Purchase #7	$31.29	7.236%	$33.5541	$33.55	$33.55	$33.60
7 purchase totals =	$1,144.81		$1,256.4197	$1,256.42	$1,256.40	$1,256.40