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	$220.83	5.581%	$233.1545	$233.15	$233.15	$233.20
Purchase #2	$200.51	6.432%	$213.4068	$213.41	$213.40	$213.40
Purchase #3	$11.48	3.597%	$11.8929	$11.89	$11.90	$11.90
Purchase #4	$116.76	12.455%	$131.3025	$131.30	$131.30	$131.30
Purchase #5	$108.91	10.197%	$120.0156	$120.02	$120.00	$120.00
Purchase #6	$132.57	9.627%	$145.3325	$145.33	$145.35	$145.30
Purchase #7	$65.51	10.692%	$72.5143	$72.51	$72.50	$72.50
7 purchase totals =	$856.57		$927.6191	$927.61	$927.60	$927.60