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	$137.32	10.529%	$151.7784	$151.78	$151.80	$151.80
Purchase #2	$180.62	6.790%	$192.8841	$192.88	$192.90	$192.90
Purchase #3	$130.76	9.675%	$143.411	$143.41	$143.40	$143.40
Purchase #4	$137.27	8.127%	$148.4259	$148.43	$148.45	$148.40
Purchase #5	$9.27	12.644%	$10.4421	$10.44	$10.45	$10.40
Purchase #6	$183.51	7.115%	$196.5667	$196.57	$196.55	$196.60
Purchase #7	$161.87	5.612%	$170.9541	$170.95	$170.95	$171.00
7 purchase totals =	$940.62		$1,014.4623	$1,014.46	$1,014.50	$1,014.50