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	$80.56	3.863%	$83.672	$83.67	$83.65	$83.70
Purchase #2	$127.92	10.825%	$141.7673	$141.77	$141.75	$141.80
Purchase #3	$179.37	5.755%	$189.6927	$189.69	$189.70	$189.70
Purchase #4	$222.44	9.278%	$243.078	$243.08	$243.10	$243.10
Purchase #5	$11.76	10.665%	$13.0142	$13.01	$13.00	$13.00
Purchase #6	$119.42	6.736%	$127.4641	$127.46	$127.45	$127.50
Purchase #7	$184.65	6.275%	$196.2368	$196.24	$196.25	$196.20
7 purchase totals =	$926.12		$994.9251	$994.92	$994.90	$995.00