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	$101.81	12.218%	$114.2491	$114.25	$114.25	$114.20
Purchase #2	$203.97	12.309%	$229.0767	$229.08	$229.10	$229.10
Purchase #3	$176.49	13.265%	$199.9014	$199.90	$199.90	$199.90
Purchase #4	$115.57	13.750%	$131.4609	$131.46	$131.45	$131.50
Purchase #5	$50.40	11.221%	$56.0554	$56.06	$56.05	$56.10
Purchase #6	$215.50	3.577%	$223.2084	$223.21	$223.20	$223.20
Purchase #7	$64.69	10.279%	$71.3395	$71.34	$71.35	$71.30
7 purchase totals =	$928.43		$1,025.2914	$1,025.30	$1,025.30	$1,025.30