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	$80.56	6.445%	$85.7521	$85.75	$85.75	$85.80
Purchase #2	$167.73	11.833%	$187.5775	$187.58	$187.60	$187.60
Purchase #3	$65.90	3.460%	$68.1801	$68.18	$68.20	$68.20
Purchase #4	$30.29	4.345%	$31.6061	$31.61	$31.60	$31.60
Purchase #5	$179.84	5.432%	$189.6089	$189.61	$189.60	$189.60
Purchase #6	$12.66	4.603%	$13.2427	$13.24	$13.25	$13.20
Purchase #7	$164.68	10.736%	$182.36	$182.36	$182.35	$182.40
7 purchase totals =	$701.66		$758.3274	$758.33	$758.35	$758.40