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	$134.53	8.593%	$146.0902	$146.09	$146.10	$146.10
Purchase #2	$151.90	8.170%	$164.3102	$164.31	$164.30	$164.30
Purchase #3	$199.93	7.360%	$214.6448	$214.64	$214.65	$214.60
Purchase #4	$187.46	4.871%	$196.5912	$196.59	$196.60	$196.60
Purchase #5	$17.83	12.750%	$20.1033	$20.10	$20.10	$20.10
Purchase #6	$210.31	11.669%	$234.8511	$234.85	$234.85	$234.90
Purchase #7	$94.34	9.423%	$103.2297	$103.23	$103.25	$103.20
7 purchase totals =	$996.30		$1,079.8205	$1,079.81	$1,079.85	$1,079.80