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	$189.59	8.348%	$205.417	$205.42	$205.40	$205.40
Purchase #2	$81.72	10.827%	$90.5678	$90.57	$90.55	$90.60
Purchase #3	$149.32	10.374%	$164.8105	$164.81	$164.80	$164.80
Purchase #4	$92.70	5.688%	$97.9728	$97.97	$97.95	$98.00
Purchase #5	$123.47	9.248%	$134.8885	$134.89	$134.90	$134.90
Purchase #6	$250.96	12.297%	$281.8206	$281.82	$281.80	$281.80
Purchase #7	$220.74	13.632%	$250.8313	$250.83	$250.85	$250.80
7 purchase totals =	$1,108.50		$1,226.3085	$1,226.31	$1,226.25	$1,226.30