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	$155.33	13.195%	$175.8258	$175.83	$175.85	$175.80
Purchase #2	$98.55	7.443%	$105.8851	$105.89	$105.90	$105.90
Purchase #3	$85.52	5.765%	$90.4502	$90.45	$90.45	$90.50
Purchase #4	$31.89	4.831%	$33.4306	$33.43	$33.45	$33.40
Purchase #5	$41.86	12.447%	$47.0703	$47.07	$47.05	$47.10
Purchase #6	$145.34	8.163%	$157.2041	$157.20	$157.20	$157.20
Purchase #7	$202.35	9.791%	$222.1621	$222.16	$222.15	$222.20
7 purchase totals =	$760.84		$832.0282	$832.03	$832.05	$832.10