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	$55.49	7.418%	$59.6062	$59.61	$59.60	$59.60
Purchase #2	$64.81	7.260%	$69.5152	$69.52	$69.50	$69.50
Purchase #3	$6.76	6.833%	$7.2219	$7.22	$7.20	$7.20
Purchase #4	$234.78	9.102%	$256.1497	$256.15	$256.15	$256.10
Purchase #5	$239.26	9.671%	$262.3988	$262.40	$262.40	$262.40
Purchase #6	$96.48	12.519%	$108.5583	$108.56	$108.55	$108.60
Purchase #7	$13.35	4.232%	$13.915	$13.92	$13.90	$13.90
7 purchase totals =	$710.93		$777.3651	$777.38	$777.30	$777.30