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	$231.43	13.355%	$262.3375	$262.34	$262.35	$262.30
Purchase #2	$134.60	11.586%	$150.1948	$150.19	$150.20	$150.20
Purchase #3	$100.87	5.776%	$106.6963	$106.70	$106.70	$106.70
Purchase #4	$181.34	13.436%	$205.7048	$205.70	$205.70	$205.70
Purchase #5	$72.86	7.417%	$78.264	$78.26	$78.25	$78.30
Purchase #6	$59.85	10.426%	$66.09	$66.09	$66.10	$66.10
Purchase #7	$171.63	11.645%	$191.6163	$191.62	$191.60	$191.60
7 purchase totals =	$952.58		$1,060.9037	$1,060.90	$1,060.90	$1,060.90