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	$188.48	4.478%	$196.9201	$196.92	$196.90	$196.90
Purchase #2	$25.51	3.240%	$26.3365	$26.34	$26.35	$26.30
Purchase #3	$27.44	8.818%	$29.8597	$29.86	$29.85	$29.90
Purchase #4	$139.78	4.273%	$145.7528	$145.75	$145.75	$145.80
Purchase #5	$245.37	11.860%	$274.4709	$274.47	$274.45	$274.50
Purchase #6	$141.28	11.502%	$157.53	$157.53	$157.55	$157.50
Purchase #7	$217.31	6.301%	$231.0027	$231.00	$231.00	$231.00
7 purchase totals =	$985.17		$1,061.8727	$1,061.87	$1,061.85	$1,061.90