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	$132.34	4.222%	$137.9274	$137.93	$137.95	$137.90
Purchase #2	$46.59	5.504%	$49.1543	$49.15	$49.15	$49.20
Purchase #3	$39.55	12.620%	$44.5412	$44.54	$44.55	$44.50
Purchase #4	$85.33	4.540%	$89.204	$89.20	$89.20	$89.20
Purchase #5	$92.71	7.736%	$99.882	$99.88	$99.90	$99.90
Purchase #6	$44.98	13.873%	$51.2201	$51.22	$51.20	$51.20
Purchase #7	$164.63	11.686%	$183.8687	$183.87	$183.85	$183.90
7 purchase totals =	$606.13		$655.7977	$655.79	$655.80	$655.80