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	$45.75	5.605%	$48.3143	$48.31	$48.30	$48.30
Purchase #2	$93.94	8.715%	$102.1269	$102.13	$102.15	$102.10
Purchase #3	$126.66	12.481%	$142.4684	$142.47	$142.45	$142.50
Purchase #4	$17.88	5.631%	$18.8868	$18.89	$18.90	$18.90
Purchase #5	$185.83	8.137%	$200.951	$200.95	$200.95	$201.00
Purchase #6	$235.87	12.303%	$264.8891	$264.89	$264.90	$264.90
Purchase #7	$145.48	10.511%	$160.7714	$160.77	$160.75	$160.80
7 purchase totals =	$851.41		$938.4079	$938.41	$938.40	$938.50