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	$18.55	4.332%	$19.3536	$19.35	$19.35	$19.40
Purchase #2	$80.92	13.686%	$91.9947	$91.99	$92.00	$92.00
Purchase #3	$52.55	10.153%	$57.8854	$57.89	$57.90	$57.90
Purchase #4	$128.37	8.758%	$139.6126	$139.61	$139.60	$139.60
Purchase #5	$114.95	10.598%	$127.1324	$127.13	$127.15	$127.10
Purchase #6	$82.47	3.491%	$85.349	$85.35	$85.35	$85.30
Purchase #7	$143.44	4.588%	$150.021	$150.02	$150.00	$150.00
7 purchase totals =	$621.25		$671.3487	$671.34	$671.35	$671.30