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	$98.69	10.620%	$109.1709	$109.17	$109.15	$109.20
Purchase #2	$74.70	5.513%	$78.8182	$78.82	$78.80	$78.80
Purchase #3	$138.56	3.188%	$142.9773	$142.98	$143.00	$143.00
Purchase #4	$76.88	13.349%	$87.1427	$87.14	$87.15	$87.10
Purchase #5	$137.26	4.366%	$143.2528	$143.25	$143.25	$143.30
Purchase #6	$148.27	13.398%	$168.1352	$168.14	$168.15	$168.10
Purchase #7	$114.37	6.274%	$121.5456	$121.55	$121.55	$121.50
7 purchase totals =	$788.73		$851.0427	$851.05	$851.05	$851.00