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	$250.85	4.774%	$262.8256	$262.83	$262.85	$262.80
Purchase #2	$156.71	3.403%	$162.0428	$162.04	$162.05	$162.00
Purchase #3	$103.74	5.537%	$109.4841	$109.48	$109.50	$109.50
Purchase #4	$196.50	7.137%	$210.5242	$210.52	$210.50	$210.50
Purchase #5	$28.37	9.177%	$30.9735	$30.97	$30.95	$31.00
Purchase #6	$20.90	4.660%	$21.8739	$21.87	$21.85	$21.90
Purchase #7	$222.88	9.433%	$243.9043	$243.90	$243.90	$243.90
7 purchase totals =	$979.95		$1,041.6284	$1,041.61	$1,041.60	$1,041.60