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	$49.76	12.245%	$55.8531	$55.85	$55.85	$55.90
Purchase #2	$40.49	6.683%	$43.1959	$43.20	$43.20	$43.20
Purchase #3	$188.72	3.873%	$196.0291	$196.03	$196.05	$196.00
Purchase #4	$18.79	3.380%	$19.4251	$19.43	$19.45	$19.40
Purchase #5	$196.43	7.860%	$211.8694	$211.87	$211.85	$211.90
Purchase #6	$28.99	12.467%	$32.6042	$32.60	$32.60	$32.60
Purchase #7	$23.79	11.204%	$26.4554	$26.46	$26.45	$26.50
7 purchase totals =	$546.97		$585.4322	$585.44	$585.45	$585.50