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	$58.35	4.684%	$61.0831	$61.08	$61.10	$61.10
Purchase #2	$105.94	11.516%	$118.1401	$118.14	$118.15	$118.10
Purchase #3	$92.64	8.837%	$100.8266	$100.83	$100.85	$100.80
Purchase #4	$96.33	8.546%	$104.5624	$104.56	$104.55	$104.60
Purchase #5	$203.63	12.204%	$228.481	$228.48	$228.50	$228.50
Purchase #6	$54.95	4.381%	$57.3574	$57.36	$57.35	$57.40
Purchase #7	$160.80	7.278%	$172.503	$172.50	$172.50	$172.50
7 purchase totals =	$772.64		$842.9536	$842.95	$843.00	$843.00