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	$173.81	3.309%	$179.5614	$179.56	$179.55	$179.60
Purchase #2	$76.77	8.799%	$83.525	$83.53	$83.55	$83.50
Purchase #3	$50.69	6.501%	$53.9854	$53.99	$54.00	$54.00
Purchase #4	$166.95	3.132%	$172.1789	$172.18	$172.20	$172.20
Purchase #5	$76.66	12.352%	$86.129	$86.13	$86.15	$86.10
Purchase #6	$18.58	8.815%	$20.2178	$20.22	$20.20	$20.20
Purchase #7	$145.61	5.696%	$153.9039	$153.90	$153.90	$153.90
7 purchase totals =	$709.07		$749.5014	$749.51	$749.55	$749.50