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	$117.71	4.549%	$123.0646	$123.06	$123.05	$123.10
Purchase #2	$80.27	12.406%	$90.2283	$90.23	$90.25	$90.20
Purchase #3	$142.30	11.700%	$158.9491	$158.95	$158.95	$158.90
Purchase #4	$193.53	6.257%	$205.6392	$205.64	$205.65	$205.60
Purchase #5	$65.31	7.570%	$70.254	$70.25	$70.25	$70.30
Purchase #6	$182.96	5.145%	$192.3733	$192.37	$192.35	$192.40
Purchase #7	$197.92	7.304%	$212.3761	$212.38	$212.40	$212.40
7 purchase totals =	$980.00		$1,052.8846	$1,052.88	$1,052.90	$1,052.90