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	$243.66	5.117%	$256.1281	$256.13	$256.15	$256.10
Purchase #2	$220.37	5.567%	$232.638	$232.64	$232.65	$232.60
Purchase #3	$190.75	4.160%	$198.6852	$198.69	$198.70	$198.70
Purchase #4	$50.59	5.505%	$53.375	$53.38	$53.40	$53.40
Purchase #5	$95.59	5.457%	$100.8063	$100.81	$100.80	$100.80
Purchase #6	$99.67	3.407%	$103.0658	$103.07	$103.05	$103.10
Purchase #7	$138.75	9.654%	$152.1449	$152.14	$152.15	$152.10
7 purchase totals =	$1,039.38		$1,096.8433	$1,096.86	$1,096.90	$1,096.80