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	$132.73	13.297%	$150.3791	$150.38	$150.40	$150.40
Purchase #2	$87.28	13.406%	$98.9808	$98.98	$99.00	$99.00
Purchase #3	$108.52	4.738%	$113.6617	$113.66	$113.65	$113.70
Purchase #4	$194.61	9.762%	$213.6078	$213.61	$213.60	$213.60
Purchase #5	$201.74	11.746%	$225.4364	$225.44	$225.45	$225.40
Purchase #6	$54.27	4.781%	$56.8646	$56.86	$56.85	$56.90
Purchase #7	$146.52	6.431%	$155.9427	$155.94	$155.95	$155.90
7 purchase totals =	$925.67		$1,014.8731	$1,014.87	$1,014.90	$1,014.90