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	$167.47	10.692%	$185.3759	$185.38	$185.40	$185.40
Purchase #2	$27.30	3.206%	$28.1752	$28.18	$28.20	$28.20
Purchase #3	$98.90	12.239%	$111.0044	$111.00	$111.00	$111.00
Purchase #4	$31.89	12.781%	$35.9659	$35.97	$35.95	$36.00
Purchase #5	$66.49	4.395%	$69.4122	$69.41	$69.40	$69.40
Purchase #6	$131.49	12.104%	$147.4055	$147.41	$147.40	$147.40
Purchase #7	$157.37	6.661%	$167.8524	$167.85	$167.85	$167.90
7 purchase totals =	$680.91		$745.1915	$745.20	$745.20	$745.30