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	$143.93	3.540%	$149.0251	$149.03	$149.05	$149.00
Purchase #2	$22.66	6.724%	$24.1837	$24.18	$24.20	$24.20
Purchase #3	$53.43	11.854%	$59.7636	$59.76	$59.75	$59.80
Purchase #4	$33.52	11.244%	$37.289	$37.29	$37.30	$37.30
Purchase #5	$238.48	6.462%	$253.8906	$253.89	$253.90	$253.90
Purchase #6	$217.45	3.390%	$224.8216	$224.82	$224.80	$224.80
Purchase #7	$144.79	11.122%	$160.8935	$160.89	$160.90	$160.90
7 purchase totals =	$854.26		$909.8671	$909.86	$909.90	$909.90