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	$229.32	7.230%	$245.8998	$245.90	$245.90	$245.90
Purchase #2	$124.71	9.179%	$136.1571	$136.16	$136.15	$136.20
Purchase #3	$71.60	13.128%	$80.9996	$81.00	$81.00	$81.00
Purchase #4	$150.77	7.830%	$162.5753	$162.58	$162.60	$162.60
Purchase #5	$74.40	12.224%	$83.4947	$83.49	$83.50	$83.50
Purchase #6	$128.30	6.370%	$136.4727	$136.47	$136.45	$136.50
Purchase #7	$148.54	5.315%	$156.4349	$156.43	$156.45	$156.40
7 purchase totals =	$927.64		$1,002.0341	$1,002.03	$1,002.05	$1,002.10