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	$193.35	9.177%	$211.0937	$211.09	$211.10	$211.10
Purchase #2	$222.32	12.334%	$249.7409	$249.74	$249.75	$249.70
Purchase #3	$55.92	10.680%	$61.8923	$61.89	$61.90	$61.90
Purchase #4	$213.91	11.665%	$238.8626	$238.86	$238.85	$238.90
Purchase #5	$90.74	8.227%	$98.2052	$98.21	$98.20	$98.20
Purchase #6	$143.89	3.477%	$148.8931	$148.89	$148.90	$148.90
Purchase #7	$191.60	3.409%	$198.1316	$198.13	$198.15	$198.10
7 purchase totals =	$1,111.73		$1,206.8194	$1,206.81	$1,206.85	$1,206.80