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	$192.97	7.279%	$207.0163	$207.02	$207.00	$207.00
Purchase #2	$100.77	13.620%	$114.4949	$114.49	$114.50	$114.50
Purchase #3	$73.97	6.521%	$78.7936	$78.79	$78.80	$78.80
Purchase #4	$48.42	10.505%	$53.5065	$53.51	$53.50	$53.50
Purchase #5	$188.45	5.301%	$198.4397	$198.44	$198.45	$198.40
Purchase #6	$67.47	6.440%	$71.8151	$71.82	$71.80	$71.80
Purchase #7	$40.64	10.446%	$44.8853	$44.89	$44.90	$44.90
7 purchase totals =	$712.69		$768.9514	$768.96	$768.95	$768.90