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	$119.57	11.446%	$133.256	$133.26	$133.25	$133.30
Purchase #2	$140.31	7.227%	$150.4502	$150.45	$150.45	$150.50
Purchase #3	$48.34	12.665%	$54.4623	$54.46	$54.45	$54.50
Purchase #4	$154.90	13.280%	$175.4707	$175.47	$175.45	$175.50
Purchase #5	$175.69	11.165%	$195.3058	$195.31	$195.30	$195.30
Purchase #6	$250.81	13.569%	$284.8424	$284.84	$284.85	$284.80
Purchase #7	$166.96	11.809%	$186.6763	$186.68	$186.70	$186.70
7 purchase totals =	$1,056.58		$1,180.4637	$1,180.47	$1,180.45	$1,180.60