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	$105.76	8.165%	$114.3953	$114.40	$114.40	$114.40
Purchase #2	$224.56	10.309%	$247.7099	$247.71	$247.70	$247.70
Purchase #3	$78.37	4.844%	$82.1662	$82.17	$82.15	$82.20
Purchase #4	$46.69	8.732%	$50.767	$50.77	$50.75	$50.80
Purchase #5	$152.65	5.403%	$160.8977	$160.90	$160.90	$160.90
Purchase #6	$10.72	7.380%	$11.5111	$11.51	$11.50	$11.50
Purchase #7	$37.63	10.678%	$41.6481	$41.65	$41.65	$41.60
7 purchase totals =	$656.38		$709.0953	$709.11	$709.05	$709.10