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	$107.91	10.804%	$119.5686	$119.57	$119.55	$119.60
Purchase #2	$165.91	5.783%	$175.5046	$175.50	$175.50	$175.50
Purchase #3	$101.59	7.714%	$109.4267	$109.43	$109.45	$109.40
Purchase #4	$135.89	10.165%	$149.7032	$149.70	$149.70	$149.70
Purchase #5	$100.34	9.172%	$109.5432	$109.54	$109.55	$109.50
Purchase #6	$27.34	5.227%	$28.7691	$28.77	$28.75	$28.80
Purchase #7	$176.92	7.295%	$189.8263	$189.83	$189.85	$189.80
7 purchase totals =	$815.90		$882.3417	$882.34	$882.35	$882.30