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	$139.44	5.615%	$147.2696	$147.27	$147.25	$147.30
Purchase #2	$130.93	11.609%	$146.1297	$146.13	$146.15	$146.10
Purchase #3	$153.78	5.661%	$162.4855	$162.49	$162.50	$162.50
Purchase #4	$57.38	10.454%	$63.3785	$63.38	$63.40	$63.40
Purchase #5	$54.71	13.119%	$61.8874	$61.89	$61.90	$61.90
Purchase #6	$58.70	9.707%	$64.398	$64.40	$64.40	$64.40
Purchase #7	$216.89	9.424%	$237.3297	$237.33	$237.35	$237.30
7 purchase totals =	$811.83		$882.8784	$882.89	$882.95	$882.90