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	$87.27	13.841%	$99.349	$99.35	$99.35	$99.30
Purchase #2	$39.75	4.523%	$41.5479	$41.55	$41.55	$41.50
Purchase #3	$42.75	12.576%	$48.1262	$48.13	$48.15	$48.10
Purchase #4	$91.84	11.315%	$102.2317	$102.23	$102.25	$102.20
Purchase #5	$179.47	6.789%	$191.6542	$191.65	$191.65	$191.70
Purchase #6	$195.89	9.814%	$215.1146	$215.11	$215.10	$215.10
Purchase #7	$214.52	4.226%	$223.5856	$223.59	$223.60	$223.60
7 purchase totals =	$851.49		$921.6092	$921.61	$921.65	$921.50