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	$181.40	10.239%	$199.9735	$199.97	$199.95	$200.00
Purchase #2	$109.39	6.640%	$116.6535	$116.65	$116.65	$116.70
Purchase #3	$52.85	7.138%	$56.6224	$56.62	$56.60	$56.60
Purchase #4	$54.87	12.140%	$61.5312	$61.53	$61.55	$61.50
Purchase #5	$174.49	3.110%	$179.9166	$179.92	$179.90	$179.90
Purchase #6	$96.60	5.113%	$101.5392	$101.54	$101.55	$101.50
Purchase #7	$223.48	13.390%	$253.404	$253.40	$253.40	$253.40
7 purchase totals =	$893.08		$969.6404	$969.63	$969.60	$969.60