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	$216.88	12.301%	$243.5584	$243.56	$243.55	$243.60
Purchase #2	$215.72	4.189%	$224.7565	$224.76	$224.75	$224.80
Purchase #3	$30.99	10.310%	$34.1851	$34.19	$34.20	$34.20
Purchase #4	$42.65	4.386%	$44.5206	$44.52	$44.50	$44.50
Purchase #5	$65.47	5.271%	$68.9209	$68.92	$68.90	$68.90
Purchase #6	$72.29	9.113%	$78.8778	$78.88	$78.90	$78.90
Purchase #7	$62.82	12.397%	$70.6078	$70.61	$70.60	$70.60
7 purchase totals =	$706.82		$765.4271	$765.44	$765.40	$765.50