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	$97.84	8.129%	$105.7934	$105.79	$105.80	$105.80
Purchase #2	$222.77	13.849%	$253.6214	$253.62	$253.60	$253.60
Purchase #3	$15.32	5.690%	$16.1917	$16.19	$16.20	$16.20
Purchase #4	$94.64	6.384%	$100.6818	$100.68	$100.70	$100.70
Purchase #5	$236.91	9.280%	$258.8952	$258.90	$258.90	$258.90
Purchase #6	$150.55	3.661%	$156.0616	$156.06	$156.05	$156.10
Purchase #7	$57.72	3.442%	$59.7067	$59.71	$59.70	$59.70
7 purchase totals =	$875.75		$950.9518	$950.95	$950.95	$951.00