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	$153.26	7.228%	$164.3376	$164.34	$164.35	$164.30
Purchase #2	$224.85	13.860%	$256.0142	$256.01	$256.00	$256.00
Purchase #3	$116.42	5.553%	$122.8848	$122.88	$122.90	$122.90
Purchase #4	$84.50	13.717%	$96.0909	$96.09	$96.10	$96.10
Purchase #5	$86.59	6.137%	$91.904	$91.90	$91.90	$91.90
Purchase #6	$52.56	13.651%	$59.735	$59.74	$59.75	$59.70
Purchase #7	$108.51	4.260%	$113.1325	$113.13	$113.15	$113.10
7 purchase totals =	$826.69		$904.0990	$904.09	$904.15	$904.00