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	$158.50	13.247%	$179.4965	$179.50	$179.50	$179.50
Purchase #2	$94.59	6.874%	$101.0921	$101.09	$101.10	$101.10
Purchase #3	$19.61	8.239%	$21.2257	$21.23	$21.25	$21.20
Purchase #4	$162.88	3.636%	$168.8023	$168.80	$168.80	$168.80
Purchase #5	$95.50	13.220%	$108.1251	$108.13	$108.15	$108.10
Purchase #6	$167.27	6.589%	$178.2914	$178.29	$178.30	$178.30
Purchase #7	$250.31	13.276%	$283.5412	$283.54	$283.55	$283.50
7 purchase totals =	$948.66		$1,040.5743	$1,040.58	$1,040.65	$1,040.50