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	$69.48	13.302%	$78.7222	$78.72	$78.70	$78.70
Purchase #2	$205.96	11.562%	$229.7731	$229.77	$229.75	$229.80
Purchase #3	$40.40	12.617%	$45.4973	$45.50	$45.50	$45.50
Purchase #4	$248.69	5.533%	$262.45	$262.45	$262.45	$262.50
Purchase #5	$193.90	9.789%	$212.8809	$212.88	$212.90	$212.90
Purchase #6	$141.70	11.671%	$158.2378	$158.24	$158.25	$158.20
Purchase #7	$192.33	7.644%	$207.0317	$207.03	$207.05	$207.00
7 purchase totals =	$1,092.46		$1,194.5930	$1,194.59	$1,194.60	$1,194.60