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	$172.67	5.121%	$181.5124	$181.51	$181.50	$181.50
Purchase #2	$185.71	7.130%	$198.9511	$198.95	$198.95	$199.00
Purchase #3	$92.45	8.505%	$100.3129	$100.31	$100.30	$100.30
Purchase #4	$83.28	7.401%	$89.4436	$89.44	$89.45	$89.40
Purchase #5	$54.90	10.355%	$60.5849	$60.58	$60.60	$60.60
Purchase #6	$166.63	6.253%	$177.0494	$177.05	$177.05	$177.00
Purchase #7	$59.81	13.654%	$67.9765	$67.98	$68.00	$68.00
7 purchase totals =	$815.45		$875.8308	$875.82	$875.85	$875.80