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	$200.77	12.292%	$225.4486	$225.45	$225.45	$225.40
Purchase #2	$19.38	7.548%	$20.8428	$20.84	$20.85	$20.80
Purchase #3	$49.41	5.143%	$51.9512	$51.95	$51.95	$52.00
Purchase #4	$189.56	7.753%	$204.2566	$204.26	$204.25	$204.30
Purchase #5	$195.79	12.205%	$219.6862	$219.69	$219.70	$219.70
Purchase #6	$82.30	10.327%	$90.7991	$90.80	$90.80	$90.80
Purchase #7	$30.86	8.425%	$33.46	$33.46	$33.45	$33.50
7 purchase totals =	$768.07		$846.4445	$846.45	$846.45	$846.50