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	$214.57	12.131%	$240.5995	$240.60	$240.60	$240.60
Purchase #2	$214.35	12.608%	$241.3752	$241.38	$241.40	$241.40
Purchase #3	$213.37	3.383%	$220.5883	$220.59	$220.60	$220.60
Purchase #4	$90.69	10.571%	$100.2768	$100.28	$100.30	$100.30
Purchase #5	$13.93	9.216%	$15.2138	$15.21	$15.20	$15.20
Purchase #6	$124.46	5.510%	$131.3177	$131.32	$131.30	$131.30
Purchase #7	$247.73	6.776%	$264.5162	$264.52	$264.50	$264.50
7 purchase totals =	$1,119.10		$1,213.8875	$1,213.90	$1,213.90	$1,213.90