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	$196.37	7.258%	$210.6225	$210.62	$210.60	$210.60
Purchase #2	$46.31	5.392%	$48.807	$48.81	$48.80	$48.80
Purchase #3	$102.81	8.508%	$111.5571	$111.56	$111.55	$111.60
Purchase #4	$195.33	6.702%	$208.421	$208.42	$208.40	$208.40
Purchase #5	$20.70	9.164%	$22.5969	$22.60	$22.60	$22.60
Purchase #6	$56.62	9.491%	$61.9938	$61.99	$62.00	$62.00
Purchase #7	$155.69	12.362%	$174.9364	$174.94	$174.95	$174.90
7 purchase totals =	$773.83		$838.9347	$838.94	$838.90	$838.90