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	$227.40	11.390%	$253.3009	$253.30	$253.30	$253.30
Purchase #2	$37.76	12.180%	$42.3592	$42.36	$42.35	$42.40
Purchase #3	$123.27	7.694%	$132.7544	$132.75	$132.75	$132.80
Purchase #4	$212.32	4.559%	$221.9997	$222.00	$222.00	$222.00
Purchase #5	$198.91	8.478%	$215.7736	$215.77	$215.75	$215.80
Purchase #6	$216.59	11.539%	$241.5823	$241.58	$241.60	$241.60
Purchase #7	$5.33	13.874%	$6.0695	$6.07	$6.05	$6.10
7 purchase totals =	$1,021.58		$1,113.8396	$1,113.83	$1,113.80	$1,114.00