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	$100.29	10.239%	$110.5587	$110.56	$110.55	$110.60
Purchase #2	$156.76	12.663%	$176.6105	$176.61	$176.60	$176.60
Purchase #3	$32.37	7.172%	$34.6916	$34.69	$34.70	$34.70
Purchase #4	$127.69	3.732%	$132.4554	$132.46	$132.45	$132.50
Purchase #5	$40.96	11.744%	$45.7703	$45.77	$45.75	$45.80
Purchase #6	$93.42	11.320%	$103.9951	$104.00	$104.00	$104.00
Purchase #7	$232.76	13.689%	$264.6225	$264.62	$264.60	$264.60
7 purchase totals =	$784.25		$868.7041	$868.71	$868.65	$868.80