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	$188.40	6.496%	$200.6385	$200.64	$200.65	$200.60
Purchase #2	$139.83	6.436%	$148.8295	$148.83	$148.85	$148.80
Purchase #3	$199.51	6.563%	$212.6038	$212.60	$212.60	$212.60
Purchase #4	$168.44	12.282%	$189.1278	$189.13	$189.15	$189.10
Purchase #5	$67.45	13.428%	$76.5072	$76.51	$76.50	$76.50
Purchase #6	$184.96	10.689%	$204.7304	$204.73	$204.75	$204.70
Purchase #7	$57.37	7.264%	$61.5374	$61.54	$61.55	$61.50
7 purchase totals =	$1,005.96		$1,093.9746	$1,093.98	$1,094.05	$1,093.80