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	$243.35	4.444%	$254.1645	$254.16	$254.15	$254.20
Purchase #2	$185.31	13.151%	$209.6801	$209.68	$209.70	$209.70
Purchase #3	$66.72	8.224%	$72.2071	$72.21	$72.20	$72.20
Purchase #4	$67.66	5.459%	$71.3536	$71.35	$71.35	$71.40
Purchase #5	$8.45	5.149%	$8.8851	$8.89	$8.90	$8.90
Purchase #6	$230.60	12.219%	$258.777	$258.78	$258.80	$258.80
Purchase #7	$139.98	7.375%	$150.3035	$150.30	$150.30	$150.30
7 purchase totals =	$942.07		$1,025.3709	$1,025.37	$1,025.40	$1,025.50