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	$114.26	13.167%	$129.3046	$129.30	$129.30	$129.30
Purchase #2	$154.38	11.645%	$172.3576	$172.36	$172.35	$172.40
Purchase #3	$63.32	5.376%	$66.7241	$66.72	$66.70	$66.70
Purchase #4	$245.87	6.667%	$262.2622	$262.26	$262.25	$262.30
Purchase #5	$203.39	12.362%	$228.5331	$228.53	$228.55	$228.50
Purchase #6	$93.34	6.717%	$99.6096	$99.61	$99.60	$99.60
Purchase #7	$92.93	10.154%	$102.3661	$102.37	$102.35	$102.40
7 purchase totals =	$967.49		$1,061.1573	$1,061.15	$1,061.10	$1,061.20