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	$96.48	12.783%	$108.813	$108.81	$108.80	$108.80
Purchase #2	$239.98	6.302%	$255.1035	$255.10	$255.10	$255.10
Purchase #3	$99.31	13.103%	$112.3226	$112.32	$112.30	$112.30
Purchase #4	$194.50	10.610%	$215.1365	$215.14	$215.15	$215.10
Purchase #5	$170.38	9.526%	$186.6104	$186.61	$186.60	$186.60
Purchase #6	$108.59	6.826%	$116.0024	$116.00	$116.00	$116.00
Purchase #7	$250.41	4.394%	$261.413	$261.41	$261.40	$261.40
7 purchase totals =	$1,159.65		$1,255.4014	$1,255.39	$1,255.35	$1,255.30