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	$196.27	13.310%	$222.3935	$222.39	$222.40	$222.40
Purchase #2	$232.79	10.370%	$256.9303	$256.93	$256.95	$256.90
Purchase #3	$109.29	3.854%	$113.502	$113.50	$113.50	$113.50
Purchase #4	$168.33	7.102%	$180.2848	$180.28	$180.30	$180.30
Purchase #5	$145.25	7.691%	$156.4212	$156.42	$156.40	$156.40
Purchase #6	$224.85	12.595%	$253.1699	$253.17	$253.15	$253.20
Purchase #7	$92.66	11.871%	$103.6597	$103.66	$103.65	$103.70
7 purchase totals =	$1,169.44		$1,286.3614	$1,286.35	$1,286.35	$1,286.40