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	$222.46	5.521%	$234.742	$234.74	$234.75	$234.70
Purchase #2	$92.71	8.688%	$100.7646	$100.76	$100.75	$100.80
Purchase #3	$137.82	11.487%	$153.6514	$153.65	$153.65	$153.70
Purchase #4	$55.57	7.715%	$59.8572	$59.86	$59.85	$59.90
Purchase #5	$78.38	6.829%	$83.7326	$83.73	$83.75	$83.70
Purchase #6	$55.71	9.519%	$61.013	$61.01	$61.00	$61.00
Purchase #7	$178.87	11.664%	$199.7334	$199.73	$199.75	$199.70
7 purchase totals =	$821.52		$893.4942	$893.48	$893.50	$893.50