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	$16.32	6.418%	$17.3674	$17.37	$17.35	$17.40
Purchase #2	$95.25	10.264%	$105.0265	$105.03	$105.05	$105.00
Purchase #3	$219.79	11.418%	$244.8856	$244.89	$244.90	$244.90
Purchase #4	$146.72	6.774%	$156.6588	$156.66	$156.65	$156.70
Purchase #5	$54.26	9.582%	$59.4592	$59.46	$59.45	$59.50
Purchase #6	$172.75	3.815%	$179.3404	$179.34	$179.35	$179.30
Purchase #7	$45.42	8.657%	$49.352	$49.35	$49.35	$49.40
7 purchase totals =	$750.51		$812.0899	$812.10	$812.10	$812.20