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	$49.89	13.442%	$56.5962	$56.60	$56.60	$56.60
Purchase #2	$18.59	13.388%	$21.0788	$21.08	$21.10	$21.10
Purchase #3	$213.81	11.425%	$238.2378	$238.24	$238.25	$238.20
Purchase #4	$164.36	7.372%	$176.4766	$176.48	$176.50	$176.50
Purchase #5	$175.26	5.250%	$184.4612	$184.46	$184.45	$184.50
Purchase #6	$99.94	5.620%	$105.5566	$105.56	$105.55	$105.60
Purchase #7	$210.43	8.512%	$228.3418	$228.34	$228.35	$228.30
7 purchase totals =	$932.28		$1,010.7490	$1,010.76	$1,010.80	$1,010.80