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	$100.37	3.456%	$103.8388	$103.84	$103.85	$103.80
Purchase #2	$138.96	4.459%	$145.1562	$145.16	$145.15	$145.20
Purchase #3	$125.80	9.295%	$137.4931	$137.49	$137.50	$137.50
Purchase #4	$247.84	6.717%	$264.4874	$264.49	$264.50	$264.50
Purchase #5	$69.97	11.554%	$78.0543	$78.05	$78.05	$78.10
Purchase #6	$139.78	5.187%	$147.0304	$147.03	$147.05	$147.00
Purchase #7	$43.83	13.516%	$49.7541	$49.75	$49.75	$49.80
7 purchase totals =	$866.55		$925.8143	$925.81	$925.85	$925.90