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	$39.53	4.759%	$41.4112	$41.41	$41.40	$41.40
Purchase #2	$117.98	11.264%	$131.2693	$131.27	$131.25	$131.30
Purchase #3	$34.58	9.798%	$37.9681	$37.97	$37.95	$38.00
Purchase #4	$172.78	12.591%	$194.5347	$194.53	$194.55	$194.50
Purchase #5	$37.70	9.112%	$41.1352	$41.14	$41.15	$41.10
Purchase #6	$180.90	5.739%	$191.2819	$191.28	$191.30	$191.30
Purchase #7	$61.89	11.128%	$68.7771	$68.78	$68.80	$68.80
7 purchase totals =	$645.36		$706.3775	$706.38	$706.40	$706.40