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	$55.32	7.493%	$59.4651	$59.47	$59.45	$59.50
Purchase #2	$128.42	7.651%	$138.2454	$138.25	$138.25	$138.20
Purchase #3	$83.80	12.616%	$94.3722	$94.37	$94.35	$94.40
Purchase #4	$61.88	6.840%	$66.1126	$66.11	$66.10	$66.10
Purchase #5	$241.35	13.171%	$273.1382	$273.14	$273.15	$273.10
Purchase #6	$237.48	7.870%	$256.1697	$256.17	$256.15	$256.20
Purchase #7	$169.88	13.721%	$193.1892	$193.19	$193.20	$193.20
7 purchase totals =	$978.13		$1,080.6924	$1,080.70	$1,080.65	$1,080.70