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	$118.29	4.610%	$123.7432	$123.74	$123.75	$123.70
Purchase #2	$169.91	5.366%	$179.0274	$179.03	$179.05	$179.00
Purchase #3	$121.58	12.615%	$136.9173	$136.92	$136.90	$136.90
Purchase #4	$188.40	5.432%	$198.6339	$198.63	$198.65	$198.60
Purchase #5	$10.85	12.679%	$12.2257	$12.23	$12.25	$12.20
Purchase #6	$59.69	5.317%	$62.8637	$62.86	$62.85	$62.90
Purchase #7	$103.30	9.860%	$113.4854	$113.49	$113.50	$113.50
7 purchase totals =	$772.02		$826.8966	$826.90	$826.95	$826.80