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	$55.27	6.811%	$59.0344	$59.03	$59.05	$59.00
Purchase #2	$113.98	13.760%	$129.6636	$129.66	$129.65	$129.70
Purchase #3	$92.50	5.778%	$97.8447	$97.84	$97.85	$97.80
Purchase #4	$118.65	8.576%	$128.8254	$128.83	$128.85	$128.80
Purchase #5	$151.40	11.363%	$168.6036	$168.60	$168.60	$168.60
Purchase #6	$219.83	6.268%	$233.6089	$233.61	$233.60	$233.60
Purchase #7	$180.43	13.192%	$204.2323	$204.23	$204.25	$204.20
7 purchase totals =	$932.06		$1,021.8129	$1,021.80	$1,021.85	$1,021.70