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	$116.38	10.459%	$128.5522	$128.55	$128.55	$128.60
Purchase #2	$175.45	11.400%	$195.4513	$195.45	$195.45	$195.50
Purchase #3	$162.28	10.332%	$179.0468	$179.05	$179.05	$179.00
Purchase #4	$115.68	3.657%	$119.9104	$119.91	$119.90	$119.90
Purchase #5	$222.40	7.352%	$238.7508	$238.75	$238.75	$238.80
Purchase #6	$242.52	5.524%	$255.9168	$255.92	$255.90	$255.90
Purchase #7	$20.44	7.191%	$21.9098	$21.91	$21.90	$21.90
7 purchase totals =	$1,055.15		$1,139.5381	$1,139.54	$1,139.50	$1,139.60