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	$191.55	9.277%	$209.3201	$209.32	$209.30	$209.30
Purchase #2	$144.39	8.366%	$156.4697	$156.47	$156.45	$156.50
Purchase #3	$38.54	5.787%	$40.7703	$40.77	$40.75	$40.80
Purchase #4	$20.34	11.405%	$22.6598	$22.66	$22.65	$22.70
Purchase #5	$140.72	3.303%	$145.368	$145.37	$145.35	$145.40
Purchase #6	$65.69	11.690%	$73.3692	$73.37	$73.35	$73.40
Purchase #7	$116.74	7.443%	$125.429	$125.43	$125.45	$125.40
7 purchase totals =	$717.97		$773.3861	$773.39	$773.30	$773.50