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	$213.91	6.303%	$227.3927	$227.39	$227.40	$227.40
Purchase #2	$62.40	9.826%	$68.5314	$68.53	$68.55	$68.50
Purchase #3	$182.69	7.677%	$196.7151	$196.72	$196.70	$196.70
Purchase #4	$96.27	11.155%	$107.0089	$107.01	$107.00	$107.00
Purchase #5	$34.57	12.563%	$38.913	$38.91	$38.90	$38.90
Purchase #6	$138.28	9.214%	$151.0211	$151.02	$151.00	$151.00
Purchase #7	$248.33	3.407%	$256.7906	$256.79	$256.80	$256.80
7 purchase totals =	$976.45		$1,046.3728	$1,046.37	$1,046.35	$1,046.30