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	$117.41	12.444%	$132.0205	$132.02	$132.00	$132.00
Purchase #2	$110.76	11.435%	$123.4254	$123.43	$123.45	$123.40
Purchase #3	$66.49	3.610%	$68.8903	$68.89	$68.90	$68.90
Purchase #4	$38.96	5.650%	$41.1612	$41.16	$41.15	$41.20
Purchase #5	$211.92	8.520%	$229.9756	$229.98	$230.00	$230.00
Purchase #6	$36.88	9.815%	$40.4998	$40.50	$40.50	$40.50
Purchase #7	$235.28	11.190%	$261.6078	$261.61	$261.60	$261.60
7 purchase totals =	$817.70		$897.5806	$897.59	$897.60	$897.60