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	$225.60	11.218%	$250.9078	$250.91	$250.90	$250.90
Purchase #2	$14.32	13.365%	$16.2339	$16.23	$16.25	$16.20
Purchase #3	$17.53	13.530%	$19.9018	$19.90	$19.90	$19.90
Purchase #4	$89.90	6.460%	$95.7075	$95.71	$95.70	$95.70
Purchase #5	$62.26	11.796%	$69.6042	$69.60	$69.60	$69.60
Purchase #6	$141.85	11.642%	$158.3642	$158.36	$158.35	$158.40
Purchase #7	$65.78	10.326%	$72.5724	$72.57	$72.55	$72.60
7 purchase totals =	$617.24		$683.2918	$683.28	$683.25	$683.30