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	$168.71	13.662%	$191.7592	$191.76	$191.75	$191.80
Purchase #2	$188.59	4.421%	$196.9276	$196.93	$196.95	$196.90
Purchase #3	$171.36	9.173%	$187.0789	$187.08	$187.10	$187.10
Purchase #4	$29.96	5.194%	$31.5161	$31.52	$31.50	$31.50
Purchase #5	$208.93	7.635%	$224.8818	$224.88	$224.90	$224.90
Purchase #6	$6.66	13.414%	$7.5534	$7.55	$7.55	$7.60
Purchase #7	$122.53	13.152%	$138.6451	$138.65	$138.65	$138.60
7 purchase totals =	$896.74		$978.3621	$978.37	$978.40	$978.40