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	$212.76	9.297%	$232.5403	$232.54	$232.55	$232.50
Purchase #2	$179.55	5.805%	$189.9729	$189.97	$189.95	$190.00
Purchase #3	$148.27	5.131%	$155.8777	$155.88	$155.90	$155.90
Purchase #4	$7.41	6.481%	$7.8902	$7.89	$7.90	$7.90
Purchase #5	$162.29	6.208%	$172.365	$172.37	$172.35	$172.40
Purchase #6	$58.67	13.180%	$66.4027	$66.40	$66.40	$66.40
Purchase #7	$84.90	4.257%	$88.5142	$88.51	$88.50	$88.50
7 purchase totals =	$853.85		$913.5630	$913.56	$913.55	$913.60