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	$40.26	9.178%	$43.9551	$43.96	$43.95	$44.00
Purchase #2	$60.44	6.678%	$64.4762	$64.48	$64.50	$64.50
Purchase #3	$245.85	4.236%	$256.2642	$256.26	$256.25	$256.30
Purchase #4	$250.27	9.356%	$273.6853	$273.69	$273.70	$273.70
Purchase #5	$130.54	7.302%	$140.072	$140.07	$140.05	$140.10
Purchase #6	$95.43	5.616%	$100.7893	$100.79	$100.80	$100.80
Purchase #7	$182.88	8.582%	$198.5748	$198.57	$198.55	$198.60
7 purchase totals =	$1,005.67		$1,077.8169	$1,077.82	$1,077.80	$1,078.00