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	$204.89	12.384%	$230.2636	$230.26	$230.25	$230.30
Purchase #2	$234.83	12.724%	$264.7098	$264.71	$264.70	$264.70
Purchase #3	$137.40	10.356%	$151.6291	$151.63	$151.65	$151.60
Purchase #4	$126.37	6.634%	$134.7534	$134.75	$134.75	$134.80
Purchase #5	$84.71	12.871%	$95.613	$95.61	$95.60	$95.60
Purchase #6	$53.99	10.129%	$59.4586	$59.46	$59.45	$59.50
Purchase #7	$67.94	8.519%	$73.7278	$73.73	$73.75	$73.70
7 purchase totals =	$910.13		$1,010.1553	$1,010.15	$1,010.15	$1,010.20