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	$117.25	9.460%	$128.3419	$128.34	$128.35	$128.30
Purchase #2	$174.25	12.775%	$196.5104	$196.51	$196.50	$196.50
Purchase #3	$220.39	11.424%	$245.5674	$245.57	$245.55	$245.60
Purchase #4	$93.25	3.560%	$96.5697	$96.57	$96.55	$96.60
Purchase #5	$218.72	4.373%	$228.2846	$228.28	$228.30	$228.30
Purchase #6	$153.59	13.597%	$174.4736	$174.47	$174.45	$174.50
Purchase #7	$41.55	4.626%	$43.4721	$43.47	$43.45	$43.50
7 purchase totals =	$1,019.00		$1,113.2197	$1,113.21	$1,113.15	$1,113.30