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	$118.50	4.419%	$123.7365	$123.74	$123.75	$123.70
Purchase #2	$150.38	7.764%	$162.0555	$162.06	$162.05	$162.10
Purchase #3	$125.69	4.855%	$131.7922	$131.79	$131.80	$131.80
Purchase #4	$72.36	8.339%	$78.3941	$78.39	$78.40	$78.40
Purchase #5	$234.89	3.652%	$243.4682	$243.47	$243.45	$243.50
Purchase #6	$227.56	10.226%	$250.8303	$250.83	$250.85	$250.80
Purchase #7	$17.41	12.794%	$19.6374	$19.64	$19.65	$19.60
7 purchase totals =	$946.79		$1,009.9142	$1,009.92	$1,009.95	$1,009.90