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	$231.82	12.320%	$260.3802	$260.38	$260.40	$260.40
Purchase #2	$28.82	13.512%	$32.7142	$32.71	$32.70	$32.70
Purchase #3	$107.63	3.869%	$111.7942	$111.79	$111.80	$111.80
Purchase #4	$100.83	5.229%	$106.1024	$106.10	$106.10	$106.10
Purchase #5	$90.87	5.374%	$95.7534	$95.75	$95.75	$95.80
Purchase #6	$140.97	8.184%	$152.507	$152.51	$152.50	$152.50
Purchase #7	$6.93	11.732%	$7.743	$7.74	$7.75	$7.70
7 purchase totals =	$707.87		$766.9944	$766.98	$767.00	$767.00