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	$85.87	11.243%	$95.5244	$95.52	$95.50	$95.50
Purchase #2	$49.95	12.874%	$56.3806	$56.38	$56.40	$56.40
Purchase #3	$218.91	3.365%	$226.2763	$226.28	$226.30	$226.30
Purchase #4	$93.92	7.380%	$100.8513	$100.85	$100.85	$100.90
Purchase #5	$92.25	4.611%	$96.5036	$96.50	$96.50	$96.50
Purchase #6	$31.69	6.732%	$33.8234	$33.82	$33.80	$33.80
Purchase #7	$132.87	8.651%	$144.3646	$144.36	$144.35	$144.40
7 purchase totals =	$705.46		$753.7242	$753.71	$753.70	$753.80