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	$209.80	7.459%	$225.449	$225.45	$225.45	$225.40
Purchase #2	$248.54	11.381%	$276.8263	$276.83	$276.85	$276.80
Purchase #3	$53.37	13.157%	$60.3919	$60.39	$60.40	$60.40
Purchase #4	$96.53	3.539%	$99.9462	$99.95	$99.95	$99.90
Purchase #5	$96.72	3.475%	$100.081	$100.08	$100.10	$100.10
Purchase #6	$231.85	9.864%	$254.7197	$254.72	$254.70	$254.70
Purchase #7	$191.61	12.370%	$215.3122	$215.31	$215.30	$215.30
7 purchase totals =	$1,128.42		$1,232.7263	$1,232.73	$1,232.75	$1,232.60