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	$172.44	10.206%	$190.0392	$190.04	$190.05	$190.00
Purchase #2	$22.82	3.124%	$23.5329	$23.53	$23.55	$23.50
Purchase #3	$32.33	3.735%	$33.5375	$33.54	$33.55	$33.50
Purchase #4	$159.26	6.337%	$169.3523	$169.35	$169.35	$169.40
Purchase #5	$124.86	13.291%	$141.4551	$141.46	$141.45	$141.50
Purchase #6	$37.49	10.849%	$41.5573	$41.56	$41.55	$41.60
Purchase #7	$100.81	5.183%	$106.035	$106.04	$106.05	$106.00
7 purchase totals =	$650.01		$705.5093	$705.52	$705.55	$705.50