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	$203.72	6.277%	$216.5075	$216.51	$216.50	$216.50
Purchase #2	$214.68	11.520%	$239.4111	$239.41	$239.40	$239.40
Purchase #3	$16.89	8.289%	$18.29	$18.29	$18.30	$18.30
Purchase #4	$145.78	4.365%	$152.1433	$152.14	$152.15	$152.10
Purchase #5	$113.39	5.282%	$119.3793	$119.38	$119.40	$119.40
Purchase #6	$82.37	11.158%	$91.5608	$91.56	$91.55	$91.60
Purchase #7	$111.45	10.599%	$123.2626	$123.26	$123.25	$123.30
7 purchase totals =	$888.28		$960.5546	$960.55	$960.55	$960.60