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	$48.92	9.506%	$53.5703	$53.57	$53.55	$53.60
Purchase #2	$36.25	9.739%	$39.7804	$39.78	$39.80	$39.80
Purchase #3	$125.85	11.517%	$140.3441	$140.34	$140.35	$140.30
Purchase #4	$82.81	6.529%	$88.2167	$88.22	$88.20	$88.20
Purchase #5	$154.90	11.614%	$172.8901	$172.89	$172.90	$172.90
Purchase #6	$82.69	13.748%	$94.0582	$94.06	$94.05	$94.10
Purchase #7	$116.97	5.344%	$123.2209	$123.22	$123.20	$123.20
7 purchase totals =	$648.39		$712.0807	$712.08	$712.05	$712.10