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	$234.42	4.540%	$245.0627	$245.06	$245.05	$245.10
Purchase #2	$206.39	7.861%	$222.6143	$222.61	$222.60	$222.60
Purchase #3	$71.51	9.821%	$78.533	$78.53	$78.55	$78.50
Purchase #4	$203.74	13.382%	$231.0045	$231.00	$231.00	$231.00
Purchase #5	$229.65	6.141%	$243.7528	$243.75	$243.75	$243.80
Purchase #6	$203.32	12.713%	$229.1681	$229.17	$229.15	$229.20
Purchase #7	$156.81	9.572%	$171.8199	$171.82	$171.80	$171.80
7 purchase totals =	$1,305.84		$1,421.9553	$1,421.94	$1,421.90	$1,422.00