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	$233.48	12.330%	$262.2681	$262.27	$262.25	$262.30
Purchase #2	$69.89	9.228%	$76.3394	$76.34	$76.35	$76.30
Purchase #3	$179.92	4.822%	$188.5957	$188.60	$188.60	$188.60
Purchase #4	$9.86	9.295%	$10.7765	$10.78	$10.80	$10.80
Purchase #5	$78.87	8.620%	$85.6686	$85.67	$85.65	$85.70
Purchase #6	$81.75	11.706%	$91.3197	$91.32	$91.30	$91.30
Purchase #7	$222.74	10.395%	$245.8938	$245.89	$245.90	$245.90
7 purchase totals =	$876.51		$960.8618	$960.87	$960.85	$960.90