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	$107.49	5.410%	$113.3052	$113.31	$113.30	$113.30
Purchase #2	$92.96	7.129%	$99.5871	$99.59	$99.60	$99.60
Purchase #3	$172.44	7.659%	$185.6472	$185.65	$185.65	$185.60
Purchase #4	$131.74	12.779%	$148.5751	$148.58	$148.60	$148.60
Purchase #5	$222.86	11.271%	$247.9786	$247.98	$248.00	$248.00
Purchase #6	$86.77	4.165%	$90.384	$90.38	$90.40	$90.40
Purchase #7	$221.85	4.204%	$231.1766	$231.18	$231.20	$231.20
7 purchase totals =	$1,036.11		$1,116.6538	$1,116.67	$1,116.75	$1,116.70