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	$48.94	11.823%	$54.7262	$54.73	$54.75	$54.70
Purchase #2	$149.90	4.278%	$156.3127	$156.31	$156.30	$156.30
Purchase #3	$241.66	13.761%	$274.9148	$274.91	$274.90	$274.90
Purchase #4	$168.72	9.828%	$185.3018	$185.30	$185.30	$185.30
Purchase #5	$157.60	11.224%	$175.289	$175.29	$175.30	$175.30
Purchase #6	$33.82	7.811%	$36.4617	$36.46	$36.45	$36.50
Purchase #7	$28.34	3.789%	$29.4138	$29.41	$29.40	$29.40
7 purchase totals =	$828.98		$912.4200	$912.41	$912.40	$912.40