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	$82.96	6.268%	$88.1599	$88.16	$88.15	$88.20
Purchase #2	$9.36	7.556%	$10.0672	$10.07	$10.05	$10.10
Purchase #3	$99.84	12.787%	$112.6065	$112.61	$112.60	$112.60
Purchase #4	$10.89	7.315%	$11.6866	$11.69	$11.70	$11.70
Purchase #5	$70.31	12.122%	$78.833	$78.83	$78.85	$78.80
Purchase #6	$15.43	11.621%	$17.2231	$17.22	$17.20	$17.20
Purchase #7	$171.43	5.331%	$180.5689	$180.57	$180.55	$180.60
7 purchase totals =	$460.22		$499.1452	$499.15	$499.10	$499.20