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	$189.72	10.661%	$209.946	$209.95	$209.95	$209.90
Purchase #2	$60.61	8.615%	$65.8316	$65.83	$65.85	$65.80
Purchase #3	$46.72	4.403%	$48.7771	$48.78	$48.80	$48.80
Purchase #4	$84.78	5.436%	$89.3886	$89.39	$89.40	$89.40
Purchase #5	$49.66	3.319%	$51.3082	$51.31	$51.30	$51.30
Purchase #6	$45.79	11.803%	$51.1946	$51.19	$51.20	$51.20
Purchase #7	$236.65	13.257%	$268.0227	$268.02	$268.00	$268.00
7 purchase totals =	$713.93		$784.4688	$784.47	$784.50	$784.40