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	$161.72	8.480%	$175.4339	$175.43	$175.45	$175.40
Purchase #2	$223.89	7.806%	$241.3669	$241.37	$241.35	$241.40
Purchase #3	$130.59	9.306%	$142.7427	$142.74	$142.75	$142.70
Purchase #4	$100.50	5.747%	$106.2757	$106.28	$106.30	$106.30
Purchase #5	$211.98	3.300%	$218.9753	$218.98	$219.00	$219.00
Purchase #6	$28.39	12.141%	$31.8368	$31.84	$31.85	$31.80
Purchase #7	$123.42	11.150%	$137.1813	$137.18	$137.20	$137.20
7 purchase totals =	$980.49		$1,053.8126	$1,053.82	$1,053.90	$1,053.80