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	$13.53	4.751%	$14.1728	$14.17	$14.15	$14.20
Purchase #2	$150.51	13.813%	$171.2999	$171.30	$171.30	$171.30
Purchase #3	$189.41	11.343%	$210.8948	$210.89	$210.90	$210.90
Purchase #4	$163.34	5.650%	$172.5687	$172.57	$172.55	$172.60
Purchase #5	$247.61	4.803%	$259.5027	$259.50	$259.50	$259.50
Purchase #6	$34.90	13.861%	$39.7375	$39.74	$39.75	$39.70
Purchase #7	$38.42	12.685%	$43.2936	$43.29	$43.30	$43.30
7 purchase totals =	$837.72		$911.4700	$911.46	$911.45	$911.50