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	$85.86	8.146%	$92.8542	$92.85	$92.85	$92.90
Purchase #2	$146.48	12.185%	$164.3286	$164.33	$164.35	$164.30
Purchase #3	$16.57	10.337%	$18.2828	$18.28	$18.30	$18.30
Purchase #4	$108.62	9.872%	$119.343	$119.34	$119.35	$119.30
Purchase #5	$165.93	13.451%	$188.2492	$188.25	$188.25	$188.20
Purchase #6	$151.29	7.361%	$162.4265	$162.43	$162.45	$162.40
Purchase #7	$37.54	9.287%	$41.0263	$41.03	$41.05	$41.00
7 purchase totals =	$712.29		$786.5106	$786.51	$786.60	$786.40