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	$48.56	7.611%	$52.2559	$52.26	$52.25	$52.30
Purchase #2	$157.53	6.432%	$167.6623	$167.66	$167.65	$167.70
Purchase #3	$19.57	3.181%	$20.1925	$20.19	$20.20	$20.20
Purchase #4	$92.88	3.801%	$96.4104	$96.41	$96.40	$96.40
Purchase #5	$196.51	4.606%	$205.5613	$205.56	$205.55	$205.60
Purchase #6	$154.76	11.146%	$172.0095	$172.01	$172.00	$172.00
Purchase #7	$112.82	9.511%	$123.5503	$123.55	$123.55	$123.60
7 purchase totals =	$782.63		$837.6422	$837.64	$837.60	$837.80