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	$193.45	4.460%	$202.0779	$202.08	$202.10	$202.10
Purchase #2	$72.55	8.565%	$78.7639	$78.76	$78.75	$78.80
Purchase #3	$42.46	5.200%	$44.6679	$44.67	$44.65	$44.70
Purchase #4	$130.89	11.234%	$145.5942	$145.59	$145.60	$145.60
Purchase #5	$150.25	6.424%	$159.9021	$159.90	$159.90	$159.90
Purchase #6	$128.51	8.565%	$139.5169	$139.52	$139.50	$139.50
Purchase #7	$99.29	12.552%	$111.7529	$111.75	$111.75	$111.80
7 purchase totals =	$817.40		$882.2758	$882.27	$882.25	$882.40