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	$75.67	8.431%	$82.0497	$82.05	$82.05	$82.00
Purchase #2	$134.71	5.802%	$142.5259	$142.53	$142.55	$142.50
Purchase #3	$231.64	11.384%	$258.0099	$258.01	$258.00	$258.00
Purchase #4	$106.48	8.560%	$115.5947	$115.59	$115.60	$115.60
Purchase #5	$174.88	12.469%	$196.6858	$196.69	$196.70	$196.70
Purchase #6	$104.71	6.730%	$111.757	$111.76	$111.75	$111.80
Purchase #7	$161.48	5.362%	$170.1386	$170.14	$170.15	$170.10
7 purchase totals =	$989.57		$1,076.7616	$1,076.77	$1,076.80	$1,076.70