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	$132.27	10.805%	$146.5618	$146.56	$146.55	$146.60
Purchase #2	$222.87	9.703%	$244.4951	$244.50	$244.50	$244.50
Purchase #3	$65.97	9.150%	$72.0063	$72.01	$72.00	$72.00
Purchase #4	$35.92	5.323%	$37.832	$37.83	$37.85	$37.80
Purchase #5	$109.61	4.237%	$114.2542	$114.25	$114.25	$114.30
Purchase #6	$139.65	10.730%	$154.6344	$154.63	$154.65	$154.60
Purchase #7	$229.26	12.654%	$258.2706	$258.27	$258.25	$258.30
7 purchase totals =	$935.55		$1,028.0544	$1,028.05	$1,028.05	$1,028.10