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	$95.96	12.417%	$107.8754	$107.88	$107.90	$107.90
Purchase #2	$38.44	8.166%	$41.579	$41.58	$41.60	$41.60
Purchase #3	$99.93	9.190%	$109.1136	$109.11	$109.10	$109.10
Purchase #4	$125.50	5.801%	$132.7803	$132.78	$132.80	$132.80
Purchase #5	$123.49	5.462%	$130.235	$130.24	$130.25	$130.20
Purchase #6	$103.72	7.604%	$111.6069	$111.61	$111.60	$111.60
Purchase #7	$222.87	8.389%	$241.5666	$241.57	$241.55	$241.60
7 purchase totals =	$809.91		$874.7568	$874.77	$874.80	$874.80