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	$92.37	11.632%	$103.1145	$103.11	$103.10	$103.10
Purchase #2	$127.85	4.634%	$133.7746	$133.77	$133.75	$133.80
Purchase #3	$88.55	13.724%	$100.7026	$100.70	$100.70	$100.70
Purchase #4	$126.81	3.241%	$130.9199	$130.92	$130.90	$130.90
Purchase #5	$172.39	3.369%	$178.1978	$178.20	$178.20	$178.20
Purchase #6	$162.73	3.830%	$168.9626	$168.96	$168.95	$169.00
Purchase #7	$132.86	13.558%	$150.8732	$150.87	$150.85	$150.90
7 purchase totals =	$903.56		$966.5452	$966.53	$966.45	$966.60