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	$184.33	5.214%	$193.941	$193.94	$193.95	$193.90
Purchase #2	$98.90	3.600%	$102.4604	$102.46	$102.45	$102.50
Purchase #3	$37.56	12.293%	$42.1773	$42.18	$42.20	$42.20
Purchase #4	$94.73	9.654%	$103.8752	$103.88	$103.90	$103.90
Purchase #5	$241.31	7.150%	$258.5637	$258.56	$258.55	$258.60
Purchase #6	$48.45	8.245%	$52.4447	$52.44	$52.45	$52.40
Purchase #7	$203.61	6.343%	$216.525	$216.53	$216.55	$216.50
7 purchase totals =	$908.89		$969.9873	$969.99	$970.05	$970.00