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	$87.30	5.112%	$91.7628	$91.76	$91.75	$91.80
Purchase #2	$21.74	10.498%	$24.0223	$24.02	$24.00	$24.00
Purchase #3	$150.93	8.772%	$164.1696	$164.17	$164.15	$164.20
Purchase #4	$82.47	8.728%	$89.668	$89.67	$89.65	$89.70
Purchase #5	$41.84	11.175%	$46.5156	$46.52	$46.50	$46.50
Purchase #6	$48.98	4.820%	$51.3408	$51.34	$51.35	$51.30
Purchase #7	$111.64	11.553%	$124.5378	$124.54	$124.55	$124.50
7 purchase totals =	$544.90		$592.0169	$592.02	$591.95	$592.00