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	$130.42	11.732%	$145.7209	$145.72	$145.70	$145.70
Purchase #2	$159.87	11.740%	$178.6387	$178.64	$178.65	$178.60
Purchase #3	$40.57	3.841%	$42.1283	$42.13	$42.15	$42.10
Purchase #4	$19.36	8.165%	$20.9407	$20.94	$20.95	$20.90
Purchase #5	$21.78	7.792%	$23.4771	$23.48	$23.50	$23.50
Purchase #6	$236.62	7.454%	$254.2577	$254.26	$254.25	$254.30
Purchase #7	$200.27	11.231%	$222.7623	$222.76	$222.75	$222.80
7 purchase totals =	$808.89		$887.9257	$887.93	$887.95	$887.90