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	$171.48	8.558%	$186.1553	$186.16	$186.15	$186.20
Purchase #2	$176.30	9.724%	$193.4434	$193.44	$193.45	$193.40
Purchase #3	$20.59	5.561%	$21.735	$21.74	$21.75	$21.70
Purchase #4	$199.59	8.654%	$216.8625	$216.86	$216.85	$216.90
Purchase #5	$115.40	10.469%	$127.4812	$127.48	$127.50	$127.50
Purchase #6	$185.94	3.208%	$191.905	$191.91	$191.90	$191.90
Purchase #7	$95.50	5.788%	$101.0275	$101.03	$101.05	$101.00
7 purchase totals =	$964.80		$1,038.6099	$1,038.62	$1,038.65	$1,038.60