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	$67.89	8.409%	$73.5989	$73.60	$73.60	$73.60
Purchase #2	$206.51	11.850%	$230.9814	$230.98	$231.00	$231.00
Purchase #3	$249.47	3.656%	$258.5906	$258.59	$258.60	$258.60
Purchase #4	$200.77	11.414%	$223.6859	$223.69	$223.70	$223.70
Purchase #5	$19.43	7.669%	$20.9201	$20.92	$20.90	$20.90
Purchase #6	$192.86	3.402%	$199.4211	$199.42	$199.40	$199.40
Purchase #7	$167.35	4.679%	$175.1803	$175.18	$175.20	$175.20
7 purchase totals =	$1,104.28		$1,182.3783	$1,182.38	$1,182.40	$1,182.40