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	$127.59	11.341%	$142.06	$142.06	$142.05	$142.10
Purchase #2	$143.35	7.777%	$154.4983	$154.50	$154.50	$154.50
Purchase #3	$41.63	5.615%	$43.9675	$43.97	$43.95	$44.00
Purchase #4	$238.74	8.115%	$258.1138	$258.11	$258.10	$258.10
Purchase #5	$85.39	6.507%	$90.9463	$90.95	$90.95	$90.90
Purchase #6	$116.47	9.656%	$127.7163	$127.72	$127.70	$127.70
Purchase #7	$78.85	4.759%	$82.6025	$82.60	$82.60	$82.60
7 purchase totals =	$832.02		$899.9047	$899.91	$899.85	$899.90