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	$111.83	11.681%	$124.8929	$124.89	$124.90	$124.90
Purchase #2	$215.44	10.518%	$238.1	$238.10	$238.10	$238.10
Purchase #3	$17.61	3.505%	$18.2272	$18.23	$18.25	$18.20
Purchase #4	$78.75	6.392%	$83.7837	$83.78	$83.80	$83.80
Purchase #5	$228.26	8.802%	$248.3514	$248.35	$248.35	$248.40
Purchase #6	$11.47	8.433%	$12.4373	$12.44	$12.45	$12.40
Purchase #7	$37.43	3.234%	$38.6405	$38.64	$38.65	$38.60
7 purchase totals =	$700.79		$764.4330	$764.43	$764.50	$764.40