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	$235.46	5.863%	$249.265	$249.27	$249.25	$249.30
Purchase #2	$239.73	9.376%	$262.2071	$262.21	$262.20	$262.20
Purchase #3	$37.84	4.556%	$39.564	$39.56	$39.55	$39.60
Purchase #4	$114.87	3.539%	$118.9352	$118.94	$118.95	$118.90
Purchase #5	$101.57	3.643%	$105.2702	$105.27	$105.25	$105.30
Purchase #6	$209.30	9.646%	$229.4891	$229.49	$229.50	$229.50
Purchase #7	$28.72	9.803%	$31.5354	$31.54	$31.55	$31.50
7 purchase totals =	$967.49		$1,036.2660	$1,036.28	$1,036.25	$1,036.30