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	$226.57	8.540%	$245.9191	$245.92	$245.90	$245.90
Purchase #2	$62.40	3.344%	$64.4867	$64.49	$64.50	$64.50
Purchase #3	$56.31	5.550%	$59.4352	$59.44	$59.45	$59.40
Purchase #4	$59.62	3.446%	$61.6745	$61.67	$61.65	$61.70
Purchase #5	$151.82	11.231%	$168.8709	$168.87	$168.85	$168.90
Purchase #6	$201.40	4.856%	$211.18	$211.18	$211.20	$211.20
Purchase #7	$171.45	6.160%	$182.0113	$182.01	$182.00	$182.00
7 purchase totals =	$929.57		$993.5777	$993.58	$993.55	$993.60