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	$148.98	12.659%	$167.8394	$167.84	$167.85	$167.80
Purchase #2	$183.69	4.661%	$192.2518	$192.25	$192.25	$192.30
Purchase #3	$11.86	4.785%	$12.4275	$12.43	$12.45	$12.40
Purchase #4	$204.34	13.683%	$232.2998	$232.30	$232.30	$232.30
Purchase #5	$40.33	5.299%	$42.4671	$42.47	$42.45	$42.50
Purchase #6	$207.49	10.769%	$229.8346	$229.83	$229.85	$229.80
Purchase #7	$119.54	13.858%	$136.1059	$136.11	$136.10	$136.10
7 purchase totals =	$916.23		$1,013.2261	$1,013.23	$1,013.25	$1,013.20