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	$130.30	7.559%	$140.1494	$140.15	$140.15	$140.10
Purchase #2	$242.45	12.321%	$272.3223	$272.32	$272.30	$272.30
Purchase #3	$22.41	13.835%	$25.5104	$25.51	$25.50	$25.50
Purchase #4	$247.90	3.126%	$255.6494	$255.65	$255.65	$255.60
Purchase #5	$80.58	10.485%	$89.0288	$89.03	$89.05	$89.00
Purchase #6	$119.63	3.350%	$123.6376	$123.64	$123.65	$123.60
Purchase #7	$139.25	7.732%	$150.0168	$150.02	$150.00	$150.00
7 purchase totals =	$982.52		$1,056.3147	$1,056.32	$1,056.30	$1,056.10