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	$78.78	13.778%	$89.6343	$89.63	$89.65	$89.60
Purchase #2	$39.53	4.319%	$41.2373	$41.24	$41.25	$41.20
Purchase #3	$156.98	13.596%	$178.323	$178.32	$178.30	$178.30
Purchase #4	$167.90	13.794%	$191.0601	$191.06	$191.05	$191.10
Purchase #5	$36.98	12.440%	$41.5803	$41.58	$41.60	$41.60
Purchase #6	$196.80	4.665%	$205.9807	$205.98	$206.00	$206.00
Purchase #7	$169.96	8.644%	$184.6513	$184.65	$184.65	$184.70
7 purchase totals =	$846.93		$932.4670	$932.46	$932.50	$932.50