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	$120.93	5.416%	$127.4796	$127.48	$127.50	$127.50
Purchase #2	$143.39	3.592%	$148.5406	$148.54	$148.55	$148.50
Purchase #3	$21.82	5.214%	$22.9577	$22.96	$22.95	$23.00
Purchase #4	$139.46	11.352%	$155.2915	$155.29	$155.30	$155.30
Purchase #5	$219.76	9.432%	$240.4878	$240.49	$240.50	$240.50
Purchase #6	$121.31	9.254%	$132.536	$132.54	$132.55	$132.50
Purchase #7	$61.96	6.330%	$65.8821	$65.88	$65.90	$65.90
7 purchase totals =	$828.63		$893.1753	$893.18	$893.25	$893.20