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	$52.41	13.620%	$59.5482	$59.55	$59.55	$59.50
Purchase #2	$199.76	7.702%	$215.1455	$215.15	$215.15	$215.10
Purchase #3	$104.91	11.419%	$116.8897	$116.89	$116.90	$116.90
Purchase #4	$86.53	8.341%	$93.7475	$93.75	$93.75	$93.70
Purchase #5	$161.98	12.284%	$181.8776	$181.88	$181.90	$181.90
Purchase #6	$191.32	13.627%	$217.3912	$217.39	$217.40	$217.40
Purchase #7	$184.63	4.295%	$192.5599	$192.56	$192.55	$192.60
7 purchase totals =	$981.54		$1,077.1596	$1,077.17	$1,077.20	$1,077.10