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	$89.68	12.685%	$101.0559	$101.06	$101.05	$101.10
Purchase #2	$185.72	5.274%	$195.5149	$195.51	$195.50	$195.50
Purchase #3	$71.59	9.558%	$78.4326	$78.43	$78.45	$78.40
Purchase #4	$130.83	8.713%	$142.2292	$142.23	$142.25	$142.20
Purchase #5	$195.73	8.274%	$211.9247	$211.92	$211.90	$211.90
Purchase #6	$54.48	12.205%	$61.1293	$61.13	$61.15	$61.10
Purchase #7	$128.73	11.438%	$143.4541	$143.45	$143.45	$143.50
7 purchase totals =	$856.76		$933.7407	$933.73	$933.75	$933.70