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	$104.67	11.529%	$116.7374	$116.74	$116.75	$116.70
Purchase #2	$171.89	7.552%	$184.8711	$184.87	$184.85	$184.90
Purchase #3	$86.31	3.779%	$89.5717	$89.57	$89.55	$89.60
Purchase #4	$35.51	6.685%	$37.8838	$37.88	$37.90	$37.90
Purchase #5	$32.32	13.427%	$36.6596	$36.66	$36.65	$36.70
Purchase #6	$10.39	9.283%	$11.3545	$11.35	$11.35	$11.40
Purchase #7	$35.41	3.297%	$36.5775	$36.58	$36.60	$36.60
7 purchase totals =	$476.50		$513.6556	$513.65	$513.65	$513.80