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	$231.54	5.103%	$243.3555	$243.36	$243.35	$243.40
Purchase #2	$141.59	3.711%	$146.8444	$146.84	$146.85	$146.80
Purchase #3	$179.34	12.336%	$201.4634	$201.46	$201.45	$201.50
Purchase #4	$75.53	4.203%	$78.7045	$78.70	$78.70	$78.70
Purchase #5	$94.68	12.455%	$106.4724	$106.47	$106.45	$106.50
Purchase #6	$155.72	3.830%	$161.6841	$161.68	$161.70	$161.70
Purchase #7	$122.83	4.133%	$127.9066	$127.91	$127.90	$127.90
7 purchase totals =	$1,001.23		$1,066.4309	$1,066.42	$1,066.40	$1,066.50