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	$192.88	3.572%	$199.7697	$199.77	$199.75	$199.80
Purchase #2	$39.72	9.703%	$43.574	$43.57	$43.55	$43.60
Purchase #3	$14.95	12.661%	$16.8428	$16.84	$16.85	$16.80
Purchase #4	$106.27	3.111%	$109.5761	$109.58	$109.60	$109.60
Purchase #5	$233.40	6.475%	$248.5127	$248.51	$248.50	$248.50
Purchase #6	$40.64	4.832%	$42.6037	$42.60	$42.60	$42.60
Purchase #7	$234.67	11.479%	$261.6078	$261.61	$261.60	$261.60
7 purchase totals =	$862.53		$922.4868	$922.48	$922.45	$922.50