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	$28.91	11.676%	$32.2855	$32.29	$32.30	$32.30
Purchase #2	$28.37	12.435%	$31.8978	$31.90	$31.90	$31.90
Purchase #3	$139.40	9.840%	$153.117	$153.12	$153.10	$153.10
Purchase #4	$219.30	11.467%	$244.4471	$244.45	$244.45	$244.40
Purchase #5	$51.52	11.676%	$57.5355	$57.54	$57.55	$57.50
Purchase #6	$152.36	13.325%	$172.662	$172.66	$172.65	$172.70
Purchase #7	$198.78	7.228%	$213.1478	$213.15	$213.15	$213.10
7 purchase totals =	$818.64		$905.0927	$905.11	$905.10	$905.00