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	$46.37	10.369%	$51.1781	$51.18	$51.20	$51.20
Purchase #2	$228.49	12.128%	$256.2013	$256.20	$256.20	$256.20
Purchase #3	$73.30	6.480%	$78.0498	$78.05	$78.05	$78.00
Purchase #4	$233.30	7.344%	$250.4336	$250.43	$250.45	$250.40
Purchase #5	$241.89	5.598%	$255.431	$255.43	$255.45	$255.40
Purchase #6	$133.81	11.488%	$149.1821	$149.18	$149.20	$149.20
Purchase #7	$91.63	11.381%	$102.0584	$102.06	$102.05	$102.10
7 purchase totals =	$1,048.79		$1,142.5343	$1,142.53	$1,142.60	$1,142.50