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	$120.57	4.417%	$125.8956	$125.90	$125.90	$125.90
Purchase #2	$205.29	13.578%	$233.1643	$233.16	$233.15	$233.20
Purchase #3	$78.97	7.665%	$85.0231	$85.02	$85.00	$85.00
Purchase #4	$72.83	13.410%	$82.5965	$82.60	$82.60	$82.60
Purchase #5	$86.98	5.546%	$91.8039	$91.80	$91.80	$91.80
Purchase #6	$146.86	5.219%	$154.5246	$154.52	$154.50	$154.50
Purchase #7	$144.27	13.726%	$164.0725	$164.07	$164.05	$164.10
7 purchase totals =	$855.77		$937.0805	$937.07	$937.00	$937.10