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	$153.74	10.385%	$169.7059	$169.71	$169.70	$169.70
Purchase #2	$77.83	7.688%	$83.8136	$83.81	$83.80	$83.80
Purchase #3	$124.46	12.700%	$140.2664	$140.27	$140.25	$140.30
Purchase #4	$83.89	7.577%	$90.2463	$90.25	$90.25	$90.20
Purchase #5	$220.55	10.166%	$242.9711	$242.97	$242.95	$243.00
Purchase #6	$150.92	12.312%	$169.5013	$169.50	$169.50	$169.50
Purchase #7	$85.74	13.164%	$97.0268	$97.03	$97.05	$97.00
7 purchase totals =	$897.13		$993.5314	$993.54	$993.50	$993.50