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	$83.53	13.556%	$94.8533	$94.85	$94.85	$94.90
Purchase #2	$154.80	12.113%	$173.5509	$173.55	$173.55	$173.60
Purchase #3	$215.59	13.838%	$245.4233	$245.42	$245.40	$245.40
Purchase #4	$109.95	8.500%	$119.2958	$119.30	$119.30	$119.30
Purchase #5	$105.45	6.194%	$111.9816	$111.98	$112.00	$112.00
Purchase #6	$133.78	12.325%	$150.2684	$150.27	$150.25	$150.30
Purchase #7	$149.36	13.756%	$169.906	$169.91	$169.90	$169.90
7 purchase totals =	$952.46		$1,065.2793	$1,065.28	$1,065.25	$1,065.40