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	$233.42	4.246%	$243.331	$243.33	$243.35	$243.30
Purchase #2	$189.71	10.219%	$209.0965	$209.10	$209.10	$209.10
Purchase #3	$145.57	3.358%	$150.4582	$150.46	$150.45	$150.50
Purchase #4	$109.99	12.642%	$123.8949	$123.89	$123.90	$123.90
Purchase #5	$185.64	4.674%	$194.3168	$194.32	$194.30	$194.30
Purchase #6	$54.77	4.760%	$57.3771	$57.38	$57.40	$57.40
Purchase #7	$146.57	10.286%	$161.6462	$161.65	$161.65	$161.60
7 purchase totals =	$1,065.67		$1,140.1207	$1,140.13	$1,140.15	$1,140.10