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	$101.82	12.384%	$114.4294	$114.43	$114.45	$114.40
Purchase #2	$242.43	13.287%	$274.6417	$274.64	$274.65	$274.60
Purchase #3	$33.43	11.740%	$37.3547	$37.35	$37.35	$37.40
Purchase #4	$80.91	12.421%	$90.9598	$90.96	$90.95	$91.00
Purchase #5	$187.63	8.238%	$203.087	$203.09	$203.10	$203.10
Purchase #6	$116.78	9.644%	$128.0423	$128.04	$128.05	$128.00
Purchase #7	$148.25	5.672%	$156.6587	$156.66	$156.65	$156.70
7 purchase totals =	$911.25		$1,005.1736	$1,005.17	$1,005.20	$1,005.20