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	$133.27	4.507%	$139.2765	$139.28	$139.30	$139.30
Purchase #2	$104.39	12.612%	$117.5557	$117.56	$117.55	$117.60
Purchase #3	$89.63	7.241%	$96.1201	$96.12	$96.10	$96.10
Purchase #4	$192.59	12.448%	$216.5636	$216.56	$216.55	$216.60
Purchase #5	$246.84	4.720%	$258.4908	$258.49	$258.50	$258.50
Purchase #6	$51.73	4.734%	$54.1789	$54.18	$54.20	$54.20
Purchase #7	$144.52	4.402%	$150.8818	$150.88	$150.90	$150.90
7 purchase totals =	$962.97		$1,033.0674	$1,033.07	$1,033.10	$1,033.20