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	$222.93	11.198%	$247.8937	$247.89	$247.90	$247.90
Purchase #2	$223.64	7.341%	$240.0574	$240.06	$240.05	$240.10
Purchase #3	$12.37	7.482%	$13.2955	$13.30	$13.30	$13.30
Purchase #4	$125.88	6.124%	$133.5889	$133.59	$133.60	$133.60
Purchase #5	$109.76	13.832%	$124.942	$124.94	$124.95	$124.90
Purchase #6	$137.81	5.788%	$145.7864	$145.79	$145.80	$145.80
Purchase #7	$203.39	9.242%	$222.1873	$222.19	$222.20	$222.20
7 purchase totals =	$1,035.78		$1,127.7512	$1,127.76	$1,127.80	$1,127.80