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	$17.38	11.544%	$19.3863	$19.39	$19.40	$19.40
Purchase #2	$195.83	9.151%	$213.7504	$213.75	$213.75	$213.80
Purchase #3	$135.46	5.204%	$142.5093	$142.51	$142.50	$142.50
Purchase #4	$52.92	11.794%	$59.1614	$59.16	$59.15	$59.20
Purchase #5	$59.33	9.287%	$64.84	$64.84	$64.85	$64.80
Purchase #6	$239.94	11.625%	$267.833	$267.83	$267.85	$267.80
Purchase #7	$244.41	6.813%	$261.0617	$261.06	$261.05	$261.10
7 purchase totals =	$945.27		$1,028.5421	$1,028.54	$1,028.55	$1,028.60