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	$167.86	4.721%	$175.7847	$175.78	$175.80	$175.80
Purchase #2	$77.38	5.630%	$81.7365	$81.74	$81.75	$81.70
Purchase #3	$139.48	3.553%	$144.4357	$144.44	$144.45	$144.40
Purchase #4	$177.72	9.661%	$194.8895	$194.89	$194.90	$194.90
Purchase #5	$240.78	7.568%	$259.0022	$259.00	$259.00	$259.00
Purchase #6	$92.94	8.452%	$100.7953	$100.80	$100.80	$100.80
Purchase #7	$87.38	9.391%	$95.5859	$95.59	$95.60	$95.60
7 purchase totals =	$983.54		$1,052.2298	$1,052.24	$1,052.30	$1,052.20