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	$244.38	4.800%	$256.1102	$256.11	$256.10	$256.10
Purchase #2	$73.57	12.671%	$82.8921	$82.89	$82.90	$82.90
Purchase #3	$48.41	9.365%	$52.9436	$52.94	$52.95	$52.90
Purchase #4	$177.58	7.488%	$190.8772	$190.88	$190.90	$190.90
Purchase #5	$77.32	6.403%	$82.2708	$82.27	$82.25	$82.30
Purchase #6	$226.32	7.430%	$243.1356	$243.14	$243.15	$243.10
Purchase #7	$86.64	11.217%	$96.3584	$96.36	$96.35	$96.40
7 purchase totals =	$934.22		$1,004.5879	$1,004.59	$1,004.60	$1,004.60