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	$58.31	12.813%	$65.7813	$65.78	$65.80	$65.80
Purchase #2	$107.81	13.209%	$122.0506	$122.05	$122.05	$122.10
Purchase #3	$80.38	5.638%	$84.9118	$84.91	$84.90	$84.90
Purchase #4	$141.67	12.474%	$159.3419	$159.34	$159.35	$159.30
Purchase #5	$187.77	4.628%	$196.46	$196.46	$196.45	$196.50
Purchase #6	$159.28	4.518%	$166.4763	$166.48	$166.50	$166.50
Purchase #7	$243.30	13.187%	$275.384	$275.38	$275.40	$275.40
7 purchase totals =	$978.52		$1,070.4059	$1,070.40	$1,070.45	$1,070.50