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	$27.73	4.108%	$28.8691	$28.87	$28.85	$28.90
Purchase #2	$38.44	8.340%	$41.6459	$41.65	$41.65	$41.60
Purchase #3	$205.69	3.336%	$212.5518	$212.55	$212.55	$212.60
Purchase #4	$51.91	3.870%	$53.9189	$53.92	$53.90	$53.90
Purchase #5	$80.33	7.820%	$86.6118	$86.61	$86.60	$86.60
Purchase #6	$171.90	6.755%	$183.5118	$183.51	$183.50	$183.50
Purchase #7	$131.88	9.839%	$144.8557	$144.86	$144.85	$144.90
7 purchase totals =	$707.88		$751.9650	$751.97	$751.90	$752.00