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	$120.43	10.873%	$133.5244	$133.52	$133.50	$133.50
Purchase #2	$125.29	11.142%	$139.2498	$139.25	$139.25	$139.20
Purchase #3	$76.81	11.558%	$85.6877	$85.69	$85.70	$85.70
Purchase #4	$35.71	4.462%	$37.3034	$37.30	$37.30	$37.30
Purchase #5	$54.54	3.645%	$56.528	$56.53	$56.55	$56.50
Purchase #6	$105.54	6.131%	$112.0107	$112.01	$112.00	$112.00
Purchase #7	$7.49	5.816%	$7.9256	$7.93	$7.95	$7.90
7 purchase totals =	$525.81		$572.2296	$572.23	$572.25	$572.10