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	$82.97	13.678%	$94.3186	$94.32	$94.30	$94.30
Purchase #2	$231.56	3.777%	$240.306	$240.31	$240.30	$240.30
Purchase #3	$211.96	10.182%	$233.5418	$233.54	$233.55	$233.50
Purchase #4	$123.93	13.284%	$140.3929	$140.39	$140.40	$140.40
Purchase #5	$172.91	7.511%	$185.8973	$185.90	$185.90	$185.90
Purchase #6	$181.34	10.553%	$200.4768	$200.48	$200.50	$200.50
Purchase #7	$100.82	5.381%	$106.2451	$106.25	$106.25	$106.20
7 purchase totals =	$1,105.49		$1,201.1785	$1,201.19	$1,201.20	$1,201.10