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	$118.44	10.697%	$131.1095	$131.11	$131.10	$131.10
Purchase #2	$115.25	9.350%	$126.0259	$126.03	$126.05	$126.00
Purchase #3	$168.29	9.429%	$184.1581	$184.16	$184.15	$184.20
Purchase #4	$247.87	11.273%	$275.8124	$275.81	$275.80	$275.80
Purchase #5	$119.78	11.408%	$133.4445	$133.44	$133.45	$133.40
Purchase #6	$100.67	5.216%	$105.9209	$105.92	$105.90	$105.90
Purchase #7	$53.69	13.730%	$61.0616	$61.06	$61.05	$61.10
7 purchase totals =	$923.99		$1,017.5329	$1,017.53	$1,017.50	$1,017.50