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	$136.36	7.748%	$146.9252	$146.93	$146.95	$146.90
Purchase #2	$178.47	7.803%	$192.396	$192.40	$192.40	$192.40
Purchase #3	$92.26	12.634%	$103.9161	$103.92	$103.90	$103.90
Purchase #4	$228.26	11.652%	$254.8569	$254.86	$254.85	$254.90
Purchase #5	$6.89	8.800%	$7.4963	$7.50	$7.50	$7.50
Purchase #6	$147.94	13.154%	$167.4	$167.40	$167.40	$167.40
Purchase #7	$199.71	12.777%	$225.2269	$225.23	$225.25	$225.20
7 purchase totals =	$989.89		$1,098.2174	$1,098.24	$1,098.25	$1,098.20