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	$242.58	5.374%	$255.6162	$255.62	$255.60	$255.60
Purchase #2	$192.33	8.395%	$208.4761	$208.48	$208.50	$208.50
Purchase #3	$137.35	3.118%	$141.6326	$141.63	$141.65	$141.60
Purchase #4	$88.90	10.534%	$98.2647	$98.26	$98.25	$98.30
Purchase #5	$216.50	8.499%	$234.9003	$234.90	$234.90	$234.90
Purchase #6	$43.58	4.150%	$45.3886	$45.39	$45.40	$45.40
Purchase #7	$85.98	4.362%	$89.7304	$89.73	$89.75	$89.70
7 purchase totals =	$1,007.22		$1,074.0089	$1,074.01	$1,074.05	$1,074.00