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	$143.58	11.522%	$160.1233	$160.12	$160.10	$160.10
Purchase #2	$54.86	9.515%	$60.0799	$60.08	$60.10	$60.10
Purchase #3	$85.48	9.495%	$93.5963	$93.60	$93.60	$93.60
Purchase #4	$80.30	4.471%	$83.8902	$83.89	$83.90	$83.90
Purchase #5	$21.90	9.571%	$23.996	$24.00	$24.00	$24.00
Purchase #6	$156.33	10.181%	$172.246	$172.25	$172.25	$172.20
Purchase #7	$62.75	13.742%	$71.3731	$71.37	$71.35	$71.40
7 purchase totals =	$605.20		$665.3048	$665.31	$665.30	$665.30