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	$99.41	9.696%	$109.0488	$109.05	$109.05	$109.00
Purchase #2	$206.72	3.599%	$214.1599	$214.16	$214.15	$214.20
Purchase #3	$215.32	7.538%	$231.5508	$231.55	$231.55	$231.60
Purchase #4	$85.80	5.288%	$90.3371	$90.34	$90.35	$90.30
Purchase #5	$227.83	6.178%	$241.9053	$241.91	$241.90	$241.90
Purchase #6	$113.93	11.597%	$127.1425	$127.14	$127.15	$127.10
Purchase #7	$137.69	12.576%	$155.0059	$155.01	$155.00	$155.00
7 purchase totals =	$1,086.70		$1,169.1503	$1,169.16	$1,169.15	$1,169.10