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	$155.62	10.324%	$171.6862	$171.69	$171.70	$171.70
Purchase #2	$128.63	10.864%	$142.6044	$142.60	$142.60	$142.60
Purchase #3	$51.54	13.439%	$58.4665	$58.47	$58.45	$58.50
Purchase #4	$238.76	4.732%	$250.0581	$250.06	$250.05	$250.10
Purchase #5	$153.89	10.111%	$169.4498	$169.45	$169.45	$169.40
Purchase #6	$234.77	11.745%	$262.3437	$262.34	$262.35	$262.30
Purchase #7	$212.72	3.372%	$219.8929	$219.89	$219.90	$219.90
7 purchase totals =	$1,175.93		$1,274.5016	$1,274.50	$1,274.50	$1,274.50