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	$68.71	6.497%	$73.1741	$73.17	$73.15	$73.20
Purchase #2	$102.96	11.433%	$114.7314	$114.73	$114.75	$114.70
Purchase #3	$104.85	11.730%	$117.1489	$117.15	$117.15	$117.10
Purchase #4	$45.89	12.491%	$51.6221	$51.62	$51.60	$51.60
Purchase #5	$82.42	5.110%	$86.6317	$86.63	$86.65	$86.60
Purchase #6	$98.53	7.649%	$106.0666	$106.07	$106.05	$106.10
Purchase #7	$183.94	6.838%	$196.5178	$196.52	$196.50	$196.50
7 purchase totals =	$687.30		$745.8926	$745.89	$745.85	$745.80