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	$111.62	5.620%	$117.893	$117.89	$117.90	$117.90
Purchase #2	$101.54	7.710%	$109.3687	$109.37	$109.35	$109.40
Purchase #3	$53.36	10.803%	$59.1245	$59.12	$59.10	$59.10
Purchase #4	$156.87	13.825%	$178.5573	$178.56	$178.55	$178.60
Purchase #5	$201.90	11.419%	$224.955	$224.96	$224.95	$225.00
Purchase #6	$205.53	4.645%	$215.0769	$215.08	$215.10	$215.10
Purchase #7	$80.99	9.302%	$88.5237	$88.52	$88.50	$88.50
7 purchase totals =	$911.81		$993.4991	$993.50	$993.45	$993.60