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	$105.67	6.507%	$112.5459	$112.55	$112.55	$112.50
Purchase #2	$234.56	8.109%	$253.5805	$253.58	$253.60	$253.60
Purchase #3	$139.43	10.522%	$154.1008	$154.10	$154.10	$154.10
Purchase #4	$98.68	9.713%	$108.2648	$108.26	$108.25	$108.30
Purchase #5	$62.82	3.561%	$65.057	$65.06	$65.05	$65.10
Purchase #6	$16.46	11.265%	$18.3142	$18.31	$18.30	$18.30
Purchase #7	$103.36	9.687%	$113.3725	$113.37	$113.35	$113.40
7 purchase totals =	$760.98		$825.2357	$825.23	$825.20	$825.30