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	$192.32	10.548%	$212.6059	$212.61	$212.60	$212.60
Purchase #2	$191.98	12.836%	$216.6226	$216.62	$216.60	$216.60
Purchase #3	$42.76	12.277%	$48.0096	$48.01	$48.00	$48.00
Purchase #4	$51.33	6.493%	$54.6629	$54.66	$54.65	$54.70
Purchase #5	$26.60	4.627%	$27.8308	$27.83	$27.85	$27.80
Purchase #6	$28.90	8.693%	$31.4123	$31.41	$31.40	$31.40
Purchase #7	$211.66	3.174%	$218.3781	$218.38	$218.40	$218.40
7 purchase totals =	$745.55		$809.5222	$809.52	$809.50	$809.50