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	$240.33	7.855%	$259.2079	$259.21	$259.20	$259.20
Purchase #2	$223.59	3.780%	$232.0417	$232.04	$232.05	$232.00
Purchase #3	$173.84	5.192%	$182.8658	$182.87	$182.85	$182.90
Purchase #4	$204.60	3.355%	$211.4643	$211.46	$211.45	$211.50
Purchase #5	$56.96	12.173%	$63.8937	$63.89	$63.90	$63.90
Purchase #6	$34.52	7.585%	$37.1383	$37.14	$37.15	$37.10
Purchase #7	$78.43	12.777%	$88.451	$88.45	$88.45	$88.50
7 purchase totals =	$1,012.27		$1,075.0627	$1,075.06	$1,075.05	$1,075.10