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	$36.46	11.510%	$40.6565	$40.66	$40.65	$40.70
Purchase #2	$45.45	11.430%	$50.6449	$50.64	$50.65	$50.60
Purchase #3	$73.70	6.407%	$78.422	$78.42	$78.40	$78.40
Purchase #4	$99.36	10.866%	$110.1565	$110.16	$110.15	$110.20
Purchase #5	$31.64	3.107%	$32.6231	$32.62	$32.60	$32.60
Purchase #6	$149.71	7.216%	$160.5131	$160.51	$160.50	$160.50
Purchase #7	$201.37	11.720%	$224.9706	$224.97	$224.95	$225.00
7 purchase totals =	$637.69		$697.9867	$697.98	$697.90	$698.00