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	$52.96	5.504%	$55.8749	$55.87	$55.85	$55.90
Purchase #2	$144.98	4.111%	$150.9401	$150.94	$150.95	$150.90
Purchase #3	$170.68	11.210%	$189.8132	$189.81	$189.80	$189.80
Purchase #4	$126.28	12.639%	$142.2405	$142.24	$142.25	$142.20
Purchase #5	$145.72	8.772%	$158.5026	$158.50	$158.50	$158.50
Purchase #6	$205.96	3.657%	$213.492	$213.49	$213.50	$213.50
Purchase #7	$52.51	6.116%	$55.7215	$55.72	$55.70	$55.70
7 purchase totals =	$899.09		$966.5848	$966.57	$966.55	$966.50