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	$148.48	9.383%	$162.4119	$162.41	$162.40	$162.40
Purchase #2	$123.96	11.233%	$137.8844	$137.88	$137.90	$137.90
Purchase #3	$146.69	13.497%	$166.4887	$166.49	$166.50	$166.50
Purchase #4	$42.36	4.314%	$44.1874	$44.19	$44.20	$44.20
Purchase #5	$33.77	3.582%	$34.9796	$34.98	$35.00	$35.00
Purchase #6	$123.68	12.829%	$139.5469	$139.55	$139.55	$139.50
Purchase #7	$135.26	4.163%	$140.8909	$140.89	$140.90	$140.90
7 purchase totals =	$754.20		$826.3898	$826.39	$826.45	$826.40