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	$66.40	9.191%	$72.5028	$72.50	$72.50	$72.50
Purchase #2	$136.68	10.764%	$151.3922	$151.39	$151.40	$151.40
Purchase #3	$94.91	5.723%	$100.3417	$100.34	$100.35	$100.30
Purchase #4	$172.31	9.244%	$188.2383	$188.24	$188.25	$188.20
Purchase #5	$249.40	5.216%	$262.4087	$262.41	$262.40	$262.40
Purchase #6	$126.75	7.155%	$135.819	$135.82	$135.80	$135.80
Purchase #7	$179.47	6.636%	$191.3796	$191.38	$191.40	$191.40
7 purchase totals =	$1,025.92		$1,102.0823	$1,102.08	$1,102.10	$1,102.00