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	$127.63	3.192%	$131.7039	$131.70	$131.70	$131.70
Purchase #2	$218.30	8.344%	$236.515	$236.52	$236.50	$236.50
Purchase #3	$27.48	13.567%	$31.2082	$31.21	$31.20	$31.20
Purchase #4	$101.38	8.185%	$109.678	$109.68	$109.70	$109.70
Purchase #5	$54.42	9.110%	$59.3777	$59.38	$59.40	$59.40
Purchase #6	$99.94	8.484%	$108.4189	$108.42	$108.40	$108.40
Purchase #7	$156.31	11.686%	$174.5764	$174.58	$174.60	$174.60
7 purchase totals =	$785.46		$851.4781	$851.49	$851.50	$851.50