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	$150.36	8.379%	$162.9587	$162.96	$162.95	$163.00
Purchase #2	$8.96	12.813%	$10.108	$10.11	$10.10	$10.10
Purchase #3	$36.46	3.253%	$37.646	$37.65	$37.65	$37.60
Purchase #4	$242.46	4.420%	$253.1767	$253.18	$253.20	$253.20
Purchase #5	$164.47	6.781%	$175.6227	$175.62	$175.60	$175.60
Purchase #6	$37.51	12.297%	$42.1226	$42.12	$42.10	$42.10
Purchase #7	$35.90	13.836%	$40.8671	$40.87	$40.85	$40.90
7 purchase totals =	$676.12		$722.5018	$722.51	$722.45	$722.50