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	$133.65	12.512%	$150.3723	$150.37	$150.35	$150.40
Purchase #2	$215.72	11.295%	$240.0856	$240.09	$240.10	$240.10
Purchase #3	$62.72	7.813%	$67.6203	$67.62	$67.60	$67.60
Purchase #4	$93.83	10.420%	$103.6071	$103.61	$103.60	$103.60
Purchase #5	$173.36	11.660%	$193.5738	$193.57	$193.55	$193.60
Purchase #6	$225.38	10.250%	$248.4815	$248.48	$248.50	$248.50
Purchase #7	$20.74	6.513%	$22.0908	$22.09	$22.10	$22.10
7 purchase totals =	$925.40		$1,025.8314	$1,025.83	$1,025.80	$1,025.90