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	$52.83	12.290%	$59.3228	$59.32	$59.30	$59.30
Purchase #2	$224.88	3.438%	$232.6114	$232.61	$232.60	$232.60
Purchase #3	$113.39	6.652%	$120.9327	$120.93	$120.95	$120.90
Purchase #4	$78.69	8.728%	$85.5581	$85.56	$85.55	$85.60
Purchase #5	$184.77	5.193%	$194.3651	$194.37	$194.35	$194.40
Purchase #6	$60.27	4.394%	$62.9183	$62.92	$62.90	$62.90
Purchase #7	$198.88	3.695%	$206.2286	$206.23	$206.25	$206.20
7 purchase totals =	$913.71		$961.9370	$961.94	$961.90	$961.90