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	$67.75	5.292%	$71.3353	$71.34	$71.35	$71.30
Purchase #2	$82.41	10.849%	$91.3507	$91.35	$91.35	$91.40
Purchase #3	$16.26	7.208%	$17.432	$17.43	$17.45	$17.40
Purchase #4	$68.92	5.799%	$72.9167	$72.92	$72.90	$72.90
Purchase #5	$20.28	12.817%	$22.8793	$22.88	$22.90	$22.90
Purchase #6	$250.38	8.776%	$272.3533	$272.35	$272.35	$272.40
Purchase #7	$104.72	12.690%	$118.009	$118.01	$118.00	$118.00
7 purchase totals =	$610.72		$666.2763	$666.28	$666.30	$666.30