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	$104.95	4.517%	$109.6906	$109.69	$109.70	$109.70
Purchase #2	$79.68	11.721%	$89.0193	$89.02	$89.00	$89.00
Purchase #3	$184.42	4.154%	$192.0808	$192.08	$192.10	$192.10
Purchase #4	$73.43	12.231%	$82.4112	$82.41	$82.40	$82.40
Purchase #5	$41.70	7.181%	$44.6945	$44.69	$44.70	$44.70
Purchase #6	$231.82	6.332%	$246.4988	$246.50	$246.50	$246.50
Purchase #7	$241.59	12.804%	$272.5232	$272.52	$272.50	$272.50
7 purchase totals =	$957.59		$1,036.9184	$1,036.91	$1,036.90	$1,036.90