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	$136.66	4.698%	$143.0803	$143.08	$143.10	$143.10
Purchase #2	$245.28	8.821%	$266.9161	$266.92	$266.90	$266.90
Purchase #3	$47.72	12.310%	$53.5943	$53.59	$53.60	$53.60
Purchase #4	$208.35	9.378%	$227.8891	$227.89	$227.90	$227.90
Purchase #5	$199.57	12.521%	$224.5582	$224.56	$224.55	$224.60
Purchase #6	$35.33	5.651%	$37.3265	$37.33	$37.35	$37.30
Purchase #7	$93.78	8.231%	$101.499	$101.50	$101.50	$101.50
7 purchase totals =	$966.69		$1,054.8635	$1,054.87	$1,054.90	$1,054.90