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	$33.46	10.674%	$37.0315	$37.03	$37.05	$37.00
Purchase #2	$52.71	13.414%	$59.7805	$59.78	$59.80	$59.80
Purchase #3	$74.28	6.852%	$79.3697	$79.37	$79.35	$79.40
Purchase #4	$24.55	3.768%	$25.475	$25.48	$25.50	$25.50
Purchase #5	$119.69	6.800%	$127.8289	$127.83	$127.85	$127.80
Purchase #6	$133.38	10.390%	$147.2382	$147.24	$147.25	$147.20
Purchase #7	$233.42	5.464%	$246.1741	$246.17	$246.15	$246.20
7 purchase totals =	$671.49		$722.8979	$722.90	$722.95	$722.90