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	$57.29	4.494%	$59.8646	$59.86	$59.85	$59.90
Purchase #2	$242.44	9.723%	$266.0124	$266.01	$266.00	$266.00
Purchase #3	$175.71	4.458%	$183.5432	$183.54	$183.55	$183.50
Purchase #4	$115.48	11.395%	$128.6389	$128.64	$128.65	$128.60
Purchase #5	$211.46	9.398%	$231.333	$231.33	$231.35	$231.30
Purchase #6	$113.30	9.796%	$124.3989	$124.40	$124.40	$124.40
Purchase #7	$133.87	12.492%	$150.593	$150.59	$150.60	$150.60
7 purchase totals =	$1,049.55		$1,144.3840	$1,144.37	$1,144.40	$1,144.30