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	$99.58	10.390%	$109.9264	$109.93	$109.95	$109.90
Purchase #2	$227.41	10.686%	$251.711	$251.71	$251.70	$251.70
Purchase #3	$196.25	3.692%	$203.4956	$203.50	$203.50	$203.50
Purchase #4	$229.90	13.754%	$261.5204	$261.52	$261.50	$261.50
Purchase #5	$248.88	8.396%	$269.776	$269.78	$269.80	$269.80
Purchase #6	$212.32	9.172%	$231.794	$231.79	$231.80	$231.80
Purchase #7	$18.47	9.756%	$20.2719	$20.27	$20.25	$20.30
7 purchase totals =	$1,232.81		$1,348.4953	$1,348.50	$1,348.50	$1,348.50