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	$194.36	4.860%	$203.8059	$203.81	$203.80	$203.80
Purchase #2	$182.32	13.310%	$206.5868	$206.59	$206.60	$206.60
Purchase #3	$45.51	6.588%	$48.5082	$48.51	$48.50	$48.50
Purchase #4	$212.48	6.206%	$225.6665	$225.67	$225.65	$225.70
Purchase #5	$19.76	4.244%	$20.5986	$20.60	$20.60	$20.60
Purchase #6	$100.43	3.769%	$104.2152	$104.22	$104.20	$104.20
Purchase #7	$236.87	8.466%	$256.9234	$256.92	$256.90	$256.90
7 purchase totals =	$991.73		$1,066.3046	$1,066.32	$1,066.25	$1,066.30