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	$203.45	13.865%	$231.6583	$231.66	$231.65	$231.70
Purchase #2	$158.60	10.430%	$175.142	$175.14	$175.15	$175.10
Purchase #3	$69.97	12.345%	$78.6078	$78.61	$78.60	$78.60
Purchase #4	$168.45	10.124%	$185.5039	$185.50	$185.50	$185.50
Purchase #5	$94.81	5.436%	$99.9639	$99.96	$99.95	$100.00
Purchase #6	$219.71	13.568%	$249.5203	$249.52	$249.50	$249.50
Purchase #7	$23.49	13.319%	$26.6186	$26.62	$26.60	$26.60
7 purchase totals =	$938.48		$1,047.0148	$1,047.01	$1,046.95	$1,047.00