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	$51.76	4.429%	$54.0525	$54.05	$54.05	$54.10
Purchase #2	$37.45	10.802%	$41.4953	$41.50	$41.50	$41.50
Purchase #3	$158.45	7.843%	$170.8772	$170.88	$170.90	$170.90
Purchase #4	$245.37	5.201%	$258.1317	$258.13	$258.15	$258.10
Purchase #5	$209.98	13.426%	$238.1719	$238.17	$238.15	$238.20
Purchase #6	$148.25	11.868%	$165.8443	$165.84	$165.85	$165.80
Purchase #7	$65.94	11.388%	$73.4492	$73.45	$73.45	$73.40
7 purchase totals =	$917.20		$1,002.0221	$1,002.02	$1,002.05	$1,002.00