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	$193.31	7.762%	$208.3147	$208.31	$208.30	$208.30
Purchase #2	$109.69	9.295%	$119.8857	$119.89	$119.90	$119.90
Purchase #3	$197.47	12.459%	$222.0728	$222.07	$222.05	$222.10
Purchase #4	$248.77	6.243%	$264.3007	$264.30	$264.30	$264.30
Purchase #5	$169.38	6.194%	$179.8714	$179.87	$179.85	$179.90
Purchase #6	$199.31	9.754%	$218.7507	$218.75	$218.75	$218.80
Purchase #7	$220.85	13.571%	$250.8216	$250.82	$250.80	$250.80
7 purchase totals =	$1,338.78		$1,464.0176	$1,464.01	$1,463.95	$1,464.10