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	$85.79	7.450%	$92.1814	$92.18	$92.20	$92.20
Purchase #2	$185.94	7.505%	$199.8948	$199.89	$199.90	$199.90
Purchase #3	$91.73	13.216%	$103.853	$103.85	$103.85	$103.90
Purchase #4	$164.77	8.838%	$179.3324	$179.33	$179.35	$179.30
Purchase #5	$119.58	3.637%	$123.9291	$123.93	$123.95	$123.90
Purchase #6	$205.40	13.733%	$233.6076	$233.61	$233.60	$233.60
Purchase #7	$166.43	3.367%	$172.0337	$172.03	$172.05	$172.00
7 purchase totals =	$1,019.64		$1,104.8320	$1,104.82	$1,104.90	$1,104.80