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	$41.36	12.502%	$46.5308	$46.53	$46.55	$46.50
Purchase #2	$56.94	7.207%	$61.0437	$61.04	$61.05	$61.00
Purchase #3	$72.52	13.506%	$82.3146	$82.31	$82.30	$82.30
Purchase #4	$201.54	12.534%	$226.801	$226.80	$226.80	$226.80
Purchase #5	$5.95	7.124%	$6.3739	$6.37	$6.35	$6.40
Purchase #6	$17.89	8.623%	$19.4327	$19.43	$19.45	$19.40
Purchase #7	$81.36	11.668%	$90.8531	$90.85	$90.85	$90.90
7 purchase totals =	$477.56		$533.3498	$533.33	$533.35	$533.30