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	$140.69	3.662%	$145.8421	$145.84	$145.85	$145.80
Purchase #2	$221.30	13.603%	$251.4034	$251.40	$251.40	$251.40
Purchase #3	$224.32	11.852%	$250.9064	$250.91	$250.90	$250.90
Purchase #4	$137.55	13.623%	$156.2884	$156.29	$156.30	$156.30
Purchase #5	$30.26	7.795%	$32.6188	$32.62	$32.60	$32.60
Purchase #6	$166.98	3.394%	$172.6473	$172.65	$172.65	$172.60
Purchase #7	$185.42	3.340%	$191.613	$191.61	$191.60	$191.60
7 purchase totals =	$1,106.52		$1,201.3194	$1,201.32	$1,201.30	$1,201.20