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	$97.86	4.779%	$102.5367	$102.54	$102.55	$102.50
Purchase #2	$11.68	6.281%	$12.4136	$12.41	$12.40	$12.40
Purchase #3	$136.72	11.794%	$152.8448	$152.84	$152.85	$152.80
Purchase #4	$59.83	10.159%	$65.9081	$65.91	$65.90	$65.90
Purchase #5	$36.72	13.826%	$41.7969	$41.80	$41.80	$41.80
Purchase #6	$249.57	13.829%	$284.083	$284.08	$284.10	$284.10
Purchase #7	$103.63	5.261%	$109.082	$109.08	$109.10	$109.10
7 purchase totals =	$696.01		$768.6651	$768.66	$768.70	$768.60