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	$119.94	11.632%	$133.8914	$133.89	$133.90	$133.90
Purchase #2	$133.33	4.812%	$139.7458	$139.75	$139.75	$139.70
Purchase #3	$71.52	13.227%	$80.98	$80.98	$81.00	$81.00
Purchase #4	$204.61	11.418%	$227.9724	$227.97	$227.95	$228.00
Purchase #5	$130.96	6.795%	$139.8587	$139.86	$139.85	$139.90
Purchase #6	$178.46	4.866%	$187.1439	$187.14	$187.15	$187.10
Purchase #7	$106.60	7.777%	$114.8903	$114.89	$114.90	$114.90
7 purchase totals =	$945.42		$1,024.4825	$1,024.48	$1,024.50	$1,024.50