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	$160.89	7.144%	$172.384	$172.38	$172.40	$172.40
Purchase #2	$212.59	3.476%	$219.9796	$219.98	$220.00	$220.00
Purchase #3	$98.91	6.745%	$105.5815	$105.58	$105.60	$105.60
Purchase #4	$236.50	13.820%	$269.1843	$269.18	$269.20	$269.20
Purchase #5	$104.85	10.813%	$116.1874	$116.19	$116.20	$116.20
Purchase #6	$14.27	5.684%	$15.0811	$15.08	$15.10	$15.10
Purchase #7	$161.53	3.507%	$167.1949	$167.19	$167.20	$167.20
7 purchase totals =	$989.54		$1,065.5928	$1,065.58	$1,065.70	$1,065.70