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	$46.34	9.682%	$50.8266	$50.83	$50.85	$50.80
Purchase #2	$141.61	9.219%	$154.665	$154.67	$154.65	$154.70
Purchase #3	$69.98	12.744%	$78.8983	$78.90	$78.90	$78.90
Purchase #4	$42.51	9.627%	$46.6024	$46.60	$46.60	$46.60
Purchase #5	$7.26	13.729%	$8.2567	$8.26	$8.25	$8.30
Purchase #6	$66.80	8.631%	$72.5655	$72.57	$72.55	$72.60
Purchase #7	$32.80	3.641%	$33.9942	$33.99	$34.00	$34.00
7 purchase totals =	$407.30		$445.8087	$445.82	$445.80	$445.90