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	$140.37	8.750%	$152.6524	$152.65	$152.65	$152.70
Purchase #2	$41.52	9.371%	$45.4108	$45.41	$45.40	$45.40
Purchase #3	$243.28	6.839%	$259.9179	$259.92	$259.90	$259.90
Purchase #4	$102.32	3.246%	$105.6413	$105.64	$105.65	$105.60
Purchase #5	$240.30	10.730%	$266.0842	$266.08	$266.10	$266.10
Purchase #6	$83.86	6.389%	$89.2178	$89.22	$89.20	$89.20
Purchase #7	$45.76	4.358%	$47.7542	$47.75	$47.75	$47.80
7 purchase totals =	$897.41		$966.6786	$966.67	$966.65	$966.70