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	$134.34	12.226%	$150.7644	$150.76	$150.75	$150.80
Purchase #2	$126.74	5.643%	$133.8919	$133.89	$133.90	$133.90
Purchase #3	$181.52	5.400%	$191.3221	$191.32	$191.30	$191.30
Purchase #4	$69.46	13.556%	$78.876	$78.88	$78.90	$78.90
Purchase #5	$105.94	3.718%	$109.8788	$109.88	$109.90	$109.90
Purchase #6	$169.49	3.386%	$175.2289	$175.23	$175.25	$175.20
Purchase #7	$188.63	4.712%	$197.5182	$197.52	$197.50	$197.50
7 purchase totals =	$976.12		$1,037.4803	$1,037.48	$1,037.50	$1,037.50