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	$193.78	3.153%	$199.8899	$199.89	$199.90	$199.90
Purchase #2	$214.31	3.684%	$222.2052	$222.21	$222.20	$222.20
Purchase #3	$132.85	5.751%	$140.4902	$140.49	$140.50	$140.50
Purchase #4	$16.72	13.169%	$18.9219	$18.92	$18.90	$18.90
Purchase #5	$96.44	10.198%	$106.275	$106.28	$106.30	$106.30
Purchase #6	$31.37	4.832%	$32.8858	$32.89	$32.90	$32.90
Purchase #7	$53.96	3.564%	$55.8831	$55.88	$55.90	$55.90
7 purchase totals =	$739.43		$776.5511	$776.56	$776.60	$776.60