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	$220.33	11.635%	$245.9654	$245.97	$245.95	$246.00
Purchase #2	$208.72	3.715%	$216.4739	$216.47	$216.45	$216.50
Purchase #3	$150.59	3.781%	$156.2838	$156.28	$156.30	$156.30
Purchase #4	$43.79	4.342%	$45.6914	$45.69	$45.70	$45.70
Purchase #5	$62.77	12.396%	$70.551	$70.55	$70.55	$70.60
Purchase #6	$128.87	6.127%	$136.7659	$136.77	$136.75	$136.80
Purchase #7	$204.97	5.668%	$216.5877	$216.59	$216.60	$216.60
7 purchase totals =	$1,020.04		$1,088.3191	$1,088.32	$1,088.30	$1,088.50