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	$229.28	3.431%	$237.1466	$237.15	$237.15	$237.10
Purchase #2	$182.68	3.376%	$188.8473	$188.85	$188.85	$188.80
Purchase #3	$86.98	9.788%	$95.4936	$95.49	$95.50	$95.50
Purchase #4	$82.82	10.371%	$91.4093	$91.41	$91.40	$91.40
Purchase #5	$38.50	8.656%	$41.8326	$41.83	$41.85	$41.80
Purchase #6	$174.99	12.110%	$196.1813	$196.18	$196.20	$196.20
Purchase #7	$103.93	8.308%	$112.5645	$112.56	$112.55	$112.60
7 purchase totals =	$899.18		$963.4752	$963.47	$963.50	$963.40