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	$213.35	6.469%	$227.1516	$227.15	$227.15	$227.20
Purchase #2	$200.49	11.159%	$222.8627	$222.86	$222.85	$222.90
Purchase #3	$83.48	11.216%	$92.8431	$92.84	$92.85	$92.80
Purchase #4	$210.33	13.572%	$238.876	$238.88	$238.90	$238.90
Purchase #5	$57.76	10.575%	$63.8681	$63.87	$63.85	$63.90
Purchase #6	$82.30	11.610%	$91.855	$91.86	$91.85	$91.90
Purchase #7	$123.93	8.312%	$134.2311	$134.23	$134.25	$134.20
7 purchase totals =	$971.64		$1,071.6876	$1,071.69	$1,071.70	$1,071.80