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	$15.27	4.665%	$15.9823	$15.98	$16.00	$16.00
Purchase #2	$54.44	9.391%	$59.5525	$59.55	$59.55	$59.60
Purchase #3	$215.29	12.865%	$242.9871	$242.99	$243.00	$243.00
Purchase #4	$101.32	8.287%	$109.7164	$109.72	$109.70	$109.70
Purchase #5	$86.40	6.162%	$91.724	$91.72	$91.70	$91.70
Purchase #6	$182.91	4.380%	$190.9215	$190.92	$190.90	$190.90
Purchase #7	$207.55	7.267%	$222.6327	$222.63	$222.65	$222.60
7 purchase totals =	$863.18		$933.5165	$933.51	$933.50	$933.50