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	$211.41	7.179%	$226.5871	$226.59	$226.60	$226.60
Purchase #2	$144.28	12.305%	$162.0337	$162.03	$162.05	$162.00
Purchase #3	$33.77	11.507%	$37.6559	$37.66	$37.65	$37.70
Purchase #4	$134.25	10.256%	$148.0187	$148.02	$148.00	$148.00
Purchase #5	$198.39	10.451%	$219.1237	$219.12	$219.10	$219.10
Purchase #6	$53.84	5.631%	$56.8717	$56.87	$56.85	$56.90
Purchase #7	$140.52	3.819%	$145.8865	$145.89	$145.90	$145.90
7 purchase totals =	$916.46		$996.1773	$996.18	$996.15	$996.20