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	$70.67	8.439%	$76.6338	$76.63	$76.65	$76.60
Purchase #2	$45.67	13.656%	$51.9067	$51.91	$51.90	$51.90
Purchase #3	$123.40	6.688%	$131.653	$131.65	$131.65	$131.70
Purchase #4	$95.56	3.158%	$98.5778	$98.58	$98.60	$98.60
Purchase #5	$87.91	3.112%	$90.6458	$90.65	$90.65	$90.60
Purchase #6	$184.60	3.539%	$191.133	$191.13	$191.15	$191.10
Purchase #7	$11.89	5.598%	$12.5556	$12.56	$12.55	$12.60
7 purchase totals =	$619.70		$653.1057	$653.11	$653.15	$653.10