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	$76.48	8.523%	$82.9984	$83.00	$83.00	$83.00
Purchase #2	$62.79	5.199%	$66.0545	$66.05	$66.05	$66.10
Purchase #3	$156.92	5.433%	$165.4455	$165.45	$165.45	$165.40
Purchase #4	$41.62	10.191%	$45.8615	$45.86	$45.85	$45.90
Purchase #5	$174.97	12.560%	$196.9462	$196.95	$196.95	$196.90
Purchase #6	$35.65	7.851%	$38.4489	$38.45	$38.45	$38.40
Purchase #7	$130.53	7.482%	$140.2963	$140.30	$140.30	$140.30
7 purchase totals =	$678.96		$736.0513	$736.06	$736.05	$736.00