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	$198.86	4.851%	$208.5067	$208.51	$208.50	$208.50
Purchase #2	$75.91	12.665%	$85.524	$85.52	$85.50	$85.50
Purchase #3	$64.93	12.191%	$72.8456	$72.85	$72.85	$72.80
Purchase #4	$237.57	10.112%	$261.5931	$261.59	$261.60	$261.60
Purchase #5	$167.80	10.185%	$184.8904	$184.89	$184.90	$184.90
Purchase #6	$206.59	6.857%	$220.7559	$220.76	$220.75	$220.80
Purchase #7	$143.65	7.180%	$153.9641	$153.96	$153.95	$154.00
7 purchase totals =	$1,095.31		$1,188.0798	$1,188.08	$1,188.05	$1,188.10