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	$28.84	12.506%	$32.4467	$32.45	$32.45	$32.40
Purchase #2	$99.27	5.710%	$104.9383	$104.94	$104.95	$104.90
Purchase #3	$46.71	5.687%	$49.3664	$49.37	$49.35	$49.40
Purchase #4	$82.35	7.673%	$88.6687	$88.67	$88.65	$88.70
Purchase #5	$235.54	6.253%	$250.2683	$250.27	$250.25	$250.30
Purchase #6	$141.48	5.217%	$148.861	$148.86	$148.85	$148.90
Purchase #7	$92.52	8.820%	$100.6803	$100.68	$100.70	$100.70
7 purchase totals =	$726.71		$775.2297	$775.24	$775.20	$775.30