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	$22.94	4.362%	$23.9406	$23.94	$23.95	$23.90
Purchase #2	$147.77	13.755%	$168.0958	$168.10	$168.10	$168.10
Purchase #3	$190.65	13.214%	$215.8425	$215.84	$215.85	$215.80
Purchase #4	$38.70	5.757%	$40.928	$40.93	$40.95	$40.90
Purchase #5	$53.56	13.802%	$60.9524	$60.95	$60.95	$61.00
Purchase #6	$146.30	12.542%	$164.6489	$164.65	$164.65	$164.60
Purchase #7	$188.50	6.338%	$200.4471	$200.45	$200.45	$200.40
7 purchase totals =	$788.42		$874.8553	$874.86	$874.90	$874.70