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	$175.99	12.495%	$197.98	$197.98	$198.00	$198.00
Purchase #2	$74.51	10.392%	$82.2531	$82.25	$82.25	$82.30
Purchase #3	$155.42	4.743%	$162.7916	$162.79	$162.80	$162.80
Purchase #4	$115.77	9.108%	$126.3143	$126.31	$126.30	$126.30
Purchase #5	$189.58	3.637%	$196.475	$196.48	$196.50	$196.50
Purchase #6	$141.31	6.652%	$150.7099	$150.71	$150.70	$150.70
Purchase #7	$51.70	5.636%	$54.6138	$54.61	$54.60	$54.60
7 purchase totals =	$904.28		$971.1377	$971.13	$971.15	$971.20