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	$103.53	3.414%	$107.0645	$107.06	$107.05	$107.10
Purchase #2	$226.97	3.310%	$234.4827	$234.48	$234.50	$234.50
Purchase #3	$209.59	10.325%	$231.2302	$231.23	$231.25	$231.20
Purchase #4	$72.56	7.621%	$78.0898	$78.09	$78.10	$78.10
Purchase #5	$97.89	8.231%	$105.9473	$105.95	$105.95	$105.90
Purchase #6	$203.83	11.398%	$227.0625	$227.06	$227.05	$227.10
Purchase #7	$47.26	11.555%	$52.7209	$52.72	$52.70	$52.70
7 purchase totals =	$961.63		$1,036.5979	$1,036.59	$1,036.60	$1,036.60