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	$238.80	11.475%	$266.2023	$266.20	$266.20	$266.20
Purchase #2	$139.58	9.767%	$153.2128	$153.21	$153.20	$153.20
Purchase #3	$82.43	9.858%	$90.5559	$90.56	$90.55	$90.60
Purchase #4	$56.36	5.118%	$59.2445	$59.24	$59.25	$59.20
Purchase #5	$249.66	4.859%	$261.791	$261.79	$261.80	$261.80
Purchase #6	$18.56	11.462%	$20.6873	$20.69	$20.70	$20.70
Purchase #7	$106.78	13.863%	$121.5829	$121.58	$121.60	$121.60
7 purchase totals =	$892.17		$973.2767	$973.27	$973.30	$973.30