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	$200.30	9.304%	$218.9359	$218.94	$218.95	$218.90
Purchase #2	$130.73	4.400%	$136.4821	$136.48	$136.50	$136.50
Purchase #3	$143.41	13.329%	$162.5251	$162.53	$162.55	$162.50
Purchase #4	$192.52	12.278%	$216.1576	$216.16	$216.15	$216.20
Purchase #5	$146.73	7.606%	$157.8903	$157.89	$157.90	$157.90
Purchase #6	$110.79	8.762%	$120.4974	$120.50	$120.50	$120.50
Purchase #7	$226.32	7.326%	$242.9002	$242.90	$242.90	$242.90
7 purchase totals =	$1,150.80		$1,255.3886	$1,255.40	$1,255.45	$1,255.40