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	$128.91	11.302%	$143.4794	$143.48	$143.50	$143.50
Purchase #2	$133.94	4.735%	$140.2821	$140.28	$140.30	$140.30
Purchase #3	$98.70	12.549%	$111.0859	$111.09	$111.10	$111.10
Purchase #4	$218.83	11.762%	$244.5688	$244.57	$244.55	$244.60
Purchase #5	$72.43	8.776%	$78.7865	$78.79	$78.80	$78.80
Purchase #6	$42.92	9.114%	$46.8317	$46.83	$46.85	$46.80
Purchase #7	$178.44	5.692%	$188.5968	$188.60	$188.60	$188.60
7 purchase totals =	$874.17		$953.6312	$953.64	$953.70	$953.70