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	$179.31	4.415%	$187.2265	$187.23	$187.25	$187.20
Purchase #2	$145.36	5.502%	$153.3577	$153.36	$153.35	$153.40
Purchase #3	$173.65	9.290%	$189.7821	$189.78	$189.80	$189.80
Purchase #4	$92.65	7.393%	$99.4996	$99.50	$99.50	$99.50
Purchase #5	$73.31	10.444%	$80.9665	$80.97	$80.95	$81.00
Purchase #6	$108.90	3.376%	$112.5765	$112.58	$112.60	$112.60
Purchase #7	$179.48	4.457%	$187.4794	$187.48	$187.50	$187.50
7 purchase totals =	$952.66		$1,010.8883	$1,010.90	$1,010.95	$1,011.00