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	$58.52	4.721%	$61.2827	$61.28	$61.30	$61.30
Purchase #2	$44.27	8.487%	$48.0272	$48.03	$48.05	$48.00
Purchase #3	$237.97	7.349%	$255.4584	$255.46	$255.45	$255.50
Purchase #4	$187.48	8.741%	$203.8676	$203.87	$203.85	$203.90
Purchase #5	$174.31	5.461%	$183.8291	$183.83	$183.85	$183.80
Purchase #6	$116.56	7.149%	$124.8929	$124.89	$124.90	$124.90
Purchase #7	$183.75	6.401%	$195.5118	$195.51	$195.50	$195.50
7 purchase totals =	$1,002.86		$1,072.8697	$1,072.87	$1,072.90	$1,072.90