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	$172.37	4.689%	$180.4524	$180.45	$180.45	$180.50
Purchase #2	$242.73	6.828%	$259.3036	$259.30	$259.30	$259.30
Purchase #3	$33.49	4.167%	$34.8855	$34.89	$34.90	$34.90
Purchase #4	$160.71	13.180%	$181.8916	$181.89	$181.90	$181.90
Purchase #5	$206.76	5.554%	$218.2435	$218.24	$218.25	$218.20
Purchase #6	$112.66	5.626%	$118.9983	$119.00	$119.00	$119.00
Purchase #7	$74.74	3.594%	$77.4262	$77.43	$77.45	$77.40
7 purchase totals =	$1,003.46		$1,071.2011	$1,071.20	$1,071.25	$1,071.20