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	$121.63	5.186%	$127.9377	$127.94	$127.95	$127.90
Purchase #2	$188.77	5.559%	$199.2637	$199.26	$199.25	$199.30
Purchase #3	$56.74	4.200%	$59.1231	$59.12	$59.10	$59.10
Purchase #4	$245.87	11.395%	$273.8869	$273.89	$273.90	$273.90
Purchase #5	$40.50	5.737%	$42.8235	$42.82	$42.80	$42.80
Purchase #6	$220.43	5.675%	$232.9394	$232.94	$232.95	$232.90
Purchase #7	$29.64	7.796%	$31.9507	$31.95	$31.95	$32.00
7 purchase totals =	$903.58		$967.9250	$967.92	$967.90	$967.90