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	$247.42	4.865%	$259.457	$259.46	$259.45	$259.50
Purchase #2	$211.88	10.420%	$233.9579	$233.96	$233.95	$234.00
Purchase #3	$142.76	6.709%	$152.3378	$152.34	$152.35	$152.30
Purchase #4	$130.83	6.871%	$139.8193	$139.82	$139.80	$139.80
Purchase #5	$64.58	11.642%	$72.0984	$72.10	$72.10	$72.10
Purchase #6	$138.47	11.294%	$154.1088	$154.11	$154.10	$154.10
Purchase #7	$249.38	13.136%	$282.1386	$282.14	$282.15	$282.10
7 purchase totals =	$1,185.32		$1,293.9178	$1,293.93	$1,293.90	$1,293.90