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	$44.79	10.221%	$49.368	$49.37	$49.35	$49.40
Purchase #2	$160.88	13.277%	$182.24	$182.24	$182.25	$182.20
Purchase #3	$242.38	9.228%	$264.7468	$264.75	$264.75	$264.70
Purchase #4	$87.33	3.736%	$90.5926	$90.59	$90.60	$90.60
Purchase #5	$98.88	5.137%	$103.9595	$103.96	$103.95	$104.00
Purchase #6	$88.50	13.402%	$100.3608	$100.36	$100.35	$100.40
Purchase #7	$138.96	3.304%	$143.5512	$143.55	$143.55	$143.60
7 purchase totals =	$861.72		$934.8189	$934.82	$934.80	$934.90