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	$188.43	6.228%	$200.1654	$200.17	$200.15	$200.20
Purchase #2	$230.94	12.477%	$259.7544	$259.75	$259.75	$259.80
Purchase #3	$185.30	11.417%	$206.4557	$206.46	$206.45	$206.50
Purchase #4	$92.94	7.629%	$100.0304	$100.03	$100.05	$100.00
Purchase #5	$75.79	3.257%	$78.2585	$78.26	$78.25	$78.30
Purchase #6	$65.49	9.768%	$71.8871	$71.89	$71.90	$71.90
Purchase #7	$232.50	3.137%	$239.7935	$239.79	$239.80	$239.80
7 purchase totals =	$1,071.39		$1,156.3450	$1,156.35	$1,156.35	$1,156.50