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	$140.95	12.824%	$159.0254	$159.03	$159.05	$159.00
Purchase #2	$127.27	11.126%	$141.4301	$141.43	$141.45	$141.40
Purchase #3	$78.73	5.352%	$82.9436	$82.94	$82.95	$82.90
Purchase #4	$31.74	11.789%	$35.4818	$35.48	$35.50	$35.50
Purchase #5	$192.26	12.260%	$215.8311	$215.83	$215.85	$215.80
Purchase #6	$118.67	9.531%	$129.9804	$129.98	$130.00	$130.00
Purchase #7	$82.31	4.831%	$86.2864	$86.29	$86.30	$86.30
7 purchase totals =	$771.93		$850.9788	$850.98	$851.10	$850.90