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	$53.43	4.772%	$55.9797	$55.98	$56.00	$56.00
Purchase #2	$234.40	13.646%	$266.3862	$266.39	$266.40	$266.40
Purchase #3	$183.63	9.422%	$200.9316	$200.93	$200.95	$200.90
Purchase #4	$203.73	7.221%	$218.4413	$218.44	$218.45	$218.40
Purchase #5	$248.94	12.830%	$280.879	$280.88	$280.90	$280.90
Purchase #6	$104.69	7.719%	$112.771	$112.77	$112.75	$112.80
Purchase #7	$28.91	5.331%	$30.4512	$30.45	$30.45	$30.50
7 purchase totals =	$1,057.73		$1,165.8400	$1,165.84	$1,165.90	$1,165.90