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	$213.74	9.523%	$234.0945	$234.09	$234.10	$234.10
Purchase #2	$93.89	5.529%	$99.0812	$99.08	$99.10	$99.10
Purchase #3	$107.25	8.298%	$116.1496	$116.15	$116.15	$116.10
Purchase #4	$90.54	4.191%	$94.3345	$94.33	$94.35	$94.30
Purchase #5	$146.53	12.116%	$164.2836	$164.28	$164.30	$164.30
Purchase #6	$200.31	13.769%	$227.8907	$227.89	$227.90	$227.90
Purchase #7	$93.69	3.624%	$97.0853	$97.09	$97.10	$97.10
7 purchase totals =	$945.95		$1,032.9194	$1,032.91	$1,033.00	$1,032.90