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	$72.55	8.441%	$78.6739	$78.67	$78.65	$78.70
Purchase #2	$61.40	11.621%	$68.5353	$68.54	$68.55	$68.50
Purchase #3	$73.61	12.160%	$82.561	$82.56	$82.55	$82.60
Purchase #4	$147.45	4.305%	$153.7977	$153.80	$153.80	$153.80
Purchase #5	$53.58	11.843%	$59.9255	$59.93	$59.95	$59.90
Purchase #6	$221.90	7.276%	$238.0454	$238.05	$238.05	$238.00
Purchase #7	$12.65	3.621%	$13.1081	$13.11	$13.10	$13.10
7 purchase totals =	$643.14		$694.6469	$694.66	$694.65	$694.60