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	$195.46	11.347%	$217.6388	$217.64	$217.65	$217.60
Purchase #2	$42.64	6.684%	$45.4901	$45.49	$45.50	$45.50
Purchase #3	$224.73	3.165%	$231.8427	$231.84	$231.85	$231.80
Purchase #4	$64.32	5.412%	$67.801	$67.80	$67.80	$67.80
Purchase #5	$175.67	5.326%	$185.0262	$185.03	$185.05	$185.00
Purchase #6	$16.80	12.450%	$18.8916	$18.89	$18.90	$18.90
Purchase #7	$106.52	12.116%	$119.426	$119.43	$119.45	$119.40
7 purchase totals =	$826.14		$886.1164	$886.12	$886.20	$886.00