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	$98.90	6.804%	$105.6292	$105.63	$105.65	$105.60
Purchase #2	$26.31	12.294%	$29.5446	$29.54	$29.55	$29.50
Purchase #3	$27.78	12.576%	$31.2736	$31.27	$31.25	$31.30
Purchase #4	$34.54	11.694%	$38.5791	$38.58	$38.60	$38.60
Purchase #5	$213.57	7.633%	$229.8718	$229.87	$229.85	$229.90
Purchase #6	$182.38	13.114%	$206.2973	$206.30	$206.30	$206.30
Purchase #7	$221.55	7.716%	$238.6448	$238.64	$238.65	$238.60
7 purchase totals =	$805.03		$879.8404	$879.83	$879.85	$879.80