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	$249.33	5.123%	$262.1032	$262.10	$262.10	$262.10
Purchase #2	$117.77	11.761%	$131.6209	$131.62	$131.60	$131.60
Purchase #3	$68.46	9.243%	$74.7878	$74.79	$74.80	$74.80
Purchase #4	$152.69	11.364%	$170.0417	$170.04	$170.05	$170.00
Purchase #5	$78.71	9.825%	$86.4433	$86.44	$86.45	$86.40
Purchase #6	$243.32	5.455%	$256.5931	$256.59	$256.60	$256.60
Purchase #7	$125.94	3.423%	$130.2509	$130.25	$130.25	$130.30
7 purchase totals =	$1,036.22		$1,111.8409	$1,111.83	$1,111.85	$1,111.80