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	$150.79	3.457%	$156.0028	$156.00	$156.00	$156.00
Purchase #2	$166.42	11.136%	$184.9525	$184.95	$184.95	$185.00
Purchase #3	$209.97	6.460%	$223.5341	$223.53	$223.55	$223.50
Purchase #4	$27.73	4.198%	$28.8941	$28.89	$28.90	$28.90
Purchase #5	$58.96	11.123%	$65.5181	$65.52	$65.50	$65.50
Purchase #6	$136.55	10.211%	$150.4931	$150.49	$150.50	$150.50
Purchase #7	$149.94	10.828%	$166.1755	$166.18	$166.20	$166.20
7 purchase totals =	$900.36		$975.5702	$975.56	$975.60	$975.60