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	$86.77	7.236%	$93.0487	$93.05	$93.05	$93.00
Purchase #2	$132.72	8.610%	$144.1472	$144.15	$144.15	$144.10
Purchase #3	$123.86	4.555%	$129.5018	$129.50	$129.50	$129.50
Purchase #4	$184.34	11.655%	$205.8248	$205.82	$205.80	$205.80
Purchase #5	$236.46	8.376%	$256.2659	$256.27	$256.25	$256.30
Purchase #6	$56.95	3.734%	$59.0765	$59.08	$59.10	$59.10
Purchase #7	$205.68	4.774%	$215.4992	$215.50	$215.50	$215.50
7 purchase totals =	$1,026.78		$1,103.3641	$1,103.37	$1,103.35	$1,103.30