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	$47.83	8.362%	$51.8295	$51.83	$51.85	$51.80
Purchase #2	$78.78	4.788%	$82.552	$82.55	$82.55	$82.60
Purchase #3	$19.55	11.323%	$21.7636	$21.76	$21.75	$21.80
Purchase #4	$34.66	9.427%	$37.9274	$37.93	$37.95	$37.90
Purchase #5	$170.68	4.378%	$178.1524	$178.15	$178.15	$178.20
Purchase #6	$36.40	10.145%	$40.0928	$40.09	$40.10	$40.10
Purchase #7	$175.83	3.296%	$181.6254	$181.63	$181.65	$181.60
7 purchase totals =	$563.73		$593.9431	$593.94	$594.00	$594.00