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	$184.77	13.780%	$210.2313	$210.23	$210.25	$210.20
Purchase #2	$110.57	6.574%	$117.8389	$117.84	$117.85	$117.80
Purchase #3	$87.75	12.835%	$99.0127	$99.01	$99.00	$99.00
Purchase #4	$202.48	4.859%	$212.3185	$212.32	$212.30	$212.30
Purchase #5	$189.31	10.174%	$208.5704	$208.57	$208.55	$208.60
Purchase #6	$111.93	10.271%	$123.4263	$123.43	$123.45	$123.40
Purchase #7	$244.48	11.234%	$271.9449	$271.94	$271.95	$271.90
7 purchase totals =	$1,131.29		$1,243.3430	$1,243.34	$1,243.35	$1,243.20