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	$164.74	4.547%	$172.2307	$172.23	$172.25	$172.20
Purchase #2	$198.74	8.500%	$215.6329	$215.63	$215.65	$215.60
Purchase #3	$249.72	9.110%	$272.4695	$272.47	$272.45	$272.50
Purchase #4	$39.26	13.512%	$44.5648	$44.56	$44.55	$44.60
Purchase #5	$157.73	4.530%	$164.8752	$164.88	$164.90	$164.90
Purchase #6	$99.57	5.381%	$104.9279	$104.93	$104.95	$104.90
Purchase #7	$96.54	4.573%	$100.9548	$100.95	$100.95	$101.00
7 purchase totals =	$1,006.30		$1,075.6558	$1,075.65	$1,075.70	$1,075.70