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	$135.52	4.165%	$141.1644	$141.16	$141.15	$141.20
Purchase #2	$179.90	5.730%	$190.2083	$190.21	$190.20	$190.20
Purchase #3	$245.33	6.180%	$260.4914	$260.49	$260.50	$260.50
Purchase #4	$35.78	7.641%	$38.5139	$38.51	$38.50	$38.50
Purchase #5	$235.34	6.709%	$251.129	$251.13	$251.15	$251.10
Purchase #6	$169.82	5.629%	$179.3792	$179.38	$179.40	$179.40
Purchase #7	$45.46	10.755%	$50.3492	$50.35	$50.35	$50.30
7 purchase totals =	$1,047.15		$1,111.2354	$1,111.23	$1,111.25	$1,111.20