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	$93.45	4.226%	$97.3992	$97.40	$97.40	$97.40
Purchase #2	$248.28	6.280%	$263.872	$263.87	$263.85	$263.90
Purchase #3	$85.99	8.603%	$93.3877	$93.39	$93.40	$93.40
Purchase #4	$201.55	10.603%	$222.9203	$222.92	$222.90	$222.90
Purchase #5	$207.88	6.849%	$222.1177	$222.12	$222.10	$222.10
Purchase #6	$146.91	12.774%	$165.6763	$165.68	$165.70	$165.70
Purchase #7	$77.49	9.766%	$85.0577	$85.06	$85.05	$85.10
7 purchase totals =	$1,061.55		$1,150.4309	$1,150.44	$1,150.40	$1,150.50