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	$206.58	4.660%	$216.2066	$216.21	$216.20	$216.20
Purchase #2	$154.86	3.636%	$160.4907	$160.49	$160.50	$160.50
Purchase #3	$30.89	13.776%	$35.1454	$35.15	$35.15	$35.10
Purchase #4	$95.92	5.828%	$101.5102	$101.51	$101.50	$101.50
Purchase #5	$223.67	7.178%	$239.725	$239.73	$239.75	$239.70
Purchase #6	$108.32	3.286%	$111.8794	$111.88	$111.90	$111.90
Purchase #7	$152.56	6.411%	$162.3406	$162.34	$162.35	$162.30
7 purchase totals =	$972.80		$1,027.2979	$1,027.31	$1,027.35	$1,027.20