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	$163.87	7.297%	$175.8276	$175.83	$175.85	$175.80
Purchase #2	$86.31	10.529%	$95.3976	$95.40	$95.40	$95.40
Purchase #3	$143.57	5.732%	$151.7994	$151.80	$151.80	$151.80
Purchase #4	$40.82	12.761%	$46.029	$46.03	$46.05	$46.00
Purchase #5	$50.81	4.585%	$53.1396	$53.14	$53.15	$53.10
Purchase #6	$242.97	6.375%	$258.4593	$258.46	$258.45	$258.50
Purchase #7	$117.71	4.803%	$123.3636	$123.36	$123.35	$123.40
7 purchase totals =	$846.06		$904.0161	$904.02	$904.05	$904.00