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	$154.82	3.575%	$160.3548	$160.35	$160.35	$160.40
Purchase #2	$79.39	13.161%	$89.8385	$89.84	$89.85	$89.80
Purchase #3	$242.42	11.340%	$269.9104	$269.91	$269.90	$269.90
Purchase #4	$153.43	9.856%	$168.5521	$168.55	$168.55	$168.60
Purchase #5	$157.42	9.347%	$172.134	$172.13	$172.15	$172.10
Purchase #6	$38.59	8.538%	$41.8848	$41.88	$41.90	$41.90
Purchase #7	$93.41	13.327%	$105.8588	$105.86	$105.85	$105.90
7 purchase totals =	$919.48		$1,008.5334	$1,008.52	$1,008.55	$1,008.60