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	$201.59	10.672%	$223.1037	$223.10	$223.10	$223.10
Purchase #2	$229.54	10.205%	$252.9646	$252.96	$252.95	$253.00
Purchase #3	$37.54	13.145%	$42.4746	$42.47	$42.45	$42.50
Purchase #4	$179.63	9.452%	$196.6086	$196.61	$196.60	$196.60
Purchase #5	$95.45	9.210%	$104.2409	$104.24	$104.25	$104.20
Purchase #6	$218.46	5.818%	$231.17	$231.17	$231.15	$231.20
Purchase #7	$120.52	7.822%	$129.9471	$129.95	$129.95	$129.90
7 purchase totals =	$1,082.73		$1,180.5095	$1,180.50	$1,180.45	$1,180.50