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	$207.96	6.841%	$222.1865	$222.19	$222.20	$222.20
Purchase #2	$39.61	7.567%	$42.6073	$42.61	$42.60	$42.60
Purchase #3	$110.79	13.129%	$125.3356	$125.34	$125.35	$125.30
Purchase #4	$203.69	6.709%	$217.3556	$217.36	$217.35	$217.40
Purchase #5	$128.46	11.716%	$143.5104	$143.51	$143.50	$143.50
Purchase #6	$19.90	8.611%	$21.6136	$21.61	$21.60	$21.60
Purchase #7	$26.44	11.731%	$29.5417	$29.54	$29.55	$29.50
7 purchase totals =	$736.85		$802.1507	$802.16	$802.15	$802.10