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	$197.32	13.429%	$223.8181	$223.82	$223.80	$223.80
Purchase #2	$158.99	8.338%	$172.2466	$172.25	$172.25	$172.20
Purchase #3	$65.90	6.588%	$70.2415	$70.24	$70.25	$70.20
Purchase #4	$53.78	10.633%	$59.4984	$59.50	$59.50	$59.50
Purchase #5	$249.27	11.846%	$278.7985	$278.80	$278.80	$278.80
Purchase #6	$28.43	6.374%	$30.2421	$30.24	$30.25	$30.20
Purchase #7	$177.81	5.306%	$187.2446	$187.24	$187.25	$187.20
7 purchase totals =	$931.50		$1,022.0898	$1,022.09	$1,022.10	$1,021.90