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	$61.57	6.182%	$65.3763	$65.38	$65.40	$65.40
Purchase #2	$196.53	4.634%	$205.6372	$205.64	$205.65	$205.60
Purchase #3	$222.54	5.246%	$234.2144	$234.21	$234.20	$234.20
Purchase #4	$150.98	13.338%	$171.1177	$171.12	$171.10	$171.10
Purchase #5	$169.47	3.183%	$174.8642	$174.86	$174.85	$174.90
Purchase #6	$32.43	12.428%	$36.4604	$36.46	$36.45	$36.50
Purchase #7	$11.58	8.369%	$12.5491	$12.55	$12.55	$12.50
7 purchase totals =	$845.10		$900.2193	$900.22	$900.20	$900.20