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	$93.34	7.869%	$100.6849	$100.68	$100.70	$100.70
Purchase #2	$163.37	9.624%	$179.0927	$179.09	$179.10	$179.10
Purchase #3	$198.40	8.444%	$215.1529	$215.15	$215.15	$215.20
Purchase #4	$205.89	13.814%	$234.3316	$234.33	$234.35	$234.30
Purchase #5	$34.98	8.263%	$37.8704	$37.87	$37.85	$37.90
Purchase #6	$152.28	5.155%	$160.13	$160.13	$160.15	$160.10
Purchase #7	$36.77	10.416%	$40.6	$40.60	$40.60	$40.60
7 purchase totals =	$885.03		$967.8625	$967.85	$967.90	$967.90