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	$212.48	3.480%	$219.8743	$219.87	$219.85	$219.90
Purchase #2	$164.80	9.751%	$180.8696	$180.87	$180.85	$180.90
Purchase #3	$141.83	7.505%	$152.4743	$152.47	$152.45	$152.50
Purchase #4	$168.54	6.133%	$178.8766	$178.88	$178.90	$178.90
Purchase #5	$96.63	4.689%	$101.161	$101.16	$101.15	$101.20
Purchase #6	$89.68	13.193%	$101.5115	$101.51	$101.50	$101.50
Purchase #7	$37.47	5.536%	$39.5443	$39.54	$39.55	$39.50
7 purchase totals =	$911.43		$974.3116	$974.30	$974.25	$974.40