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	$174.70	9.393%	$191.1096	$191.11	$191.10	$191.10
Purchase #2	$37.27	8.418%	$40.4074	$40.41	$40.40	$40.40
Purchase #3	$99.46	9.660%	$109.0678	$109.07	$109.05	$109.10
Purchase #4	$146.98	12.360%	$165.1467	$165.15	$165.15	$165.10
Purchase #5	$68.64	13.556%	$77.9448	$77.94	$77.95	$77.90
Purchase #6	$64.74	13.721%	$73.623	$73.62	$73.60	$73.60
Purchase #7	$85.71	11.656%	$95.7004	$95.70	$95.70	$95.70
7 purchase totals =	$677.50		$752.9997	$753.00	$752.95	$752.90