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	$176.92	11.241%	$196.8076	$196.81	$196.80	$196.80
Purchase #2	$117.60	13.248%	$133.1796	$133.18	$133.20	$133.20
Purchase #3	$57.29	5.444%	$60.4089	$60.41	$60.40	$60.40
Purchase #4	$147.73	4.166%	$153.8844	$153.88	$153.90	$153.90
Purchase #5	$205.83	8.296%	$222.9057	$222.91	$222.90	$222.90
Purchase #6	$39.76	3.135%	$41.0065	$41.01	$41.00	$41.00
Purchase #7	$86.26	3.649%	$89.4076	$89.41	$89.40	$89.40
7 purchase totals =	$831.39		$897.6003	$897.61	$897.60	$897.60