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	$92.72	13.596%	$105.3262	$105.33	$105.35	$105.30
Purchase #2	$227.38	10.735%	$251.7892	$251.79	$251.80	$251.80
Purchase #3	$57.81	3.176%	$59.646	$59.65	$59.65	$59.60
Purchase #4	$61.83	8.379%	$67.0107	$67.01	$67.00	$67.00
Purchase #5	$159.33	11.445%	$177.5653	$177.57	$177.55	$177.60
Purchase #6	$171.95	3.648%	$178.2227	$178.22	$178.20	$178.20
Purchase #7	$46.80	3.250%	$48.321	$48.32	$48.30	$48.30
7 purchase totals =	$817.82		$887.8811	$887.89	$887.85	$887.80