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	$173.93	8.225%	$188.2357	$188.24	$188.25	$188.20
Purchase #2	$204.44	12.435%	$229.8621	$229.86	$229.85	$229.90
Purchase #3	$63.90	4.184%	$66.5736	$66.57	$66.55	$66.60
Purchase #4	$129.39	7.295%	$138.829	$138.83	$138.85	$138.80
Purchase #5	$121.98	4.861%	$127.9094	$127.91	$127.90	$127.90
Purchase #6	$154.26	13.269%	$174.7288	$174.73	$174.75	$174.70
Purchase #7	$95.82	10.454%	$105.837	$105.84	$105.85	$105.80
7 purchase totals =	$943.72		$1,031.9756	$1,031.98	$1,032.00	$1,031.90