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	$189.77	3.786%	$196.9547	$196.95	$196.95	$197.00
Purchase #2	$142.83	4.186%	$148.8089	$148.81	$148.80	$148.80
Purchase #3	$214.97	12.790%	$242.4647	$242.46	$242.45	$242.50
Purchase #4	$164.94	8.590%	$179.1083	$179.11	$179.10	$179.10
Purchase #5	$122.41	5.235%	$128.8182	$128.82	$128.80	$128.80
Purchase #6	$93.87	12.504%	$105.6075	$105.61	$105.60	$105.60
Purchase #7	$219.50	6.211%	$233.1331	$233.13	$233.15	$233.10
7 purchase totals =	$1,148.29		$1,234.8954	$1,234.89	$1,234.85	$1,234.90