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	$214.94	6.791%	$229.5366	$229.54	$229.55	$229.50
Purchase #2	$85.28	13.180%	$96.5199	$96.52	$96.50	$96.50
Purchase #3	$54.96	5.254%	$57.8476	$57.85	$57.85	$57.80
Purchase #4	$162.74	3.429%	$168.3204	$168.32	$168.30	$168.30
Purchase #5	$238.50	11.761%	$266.55	$266.55	$266.55	$266.60
Purchase #6	$93.86	6.746%	$100.1918	$100.19	$100.20	$100.20
Purchase #7	$11.31	4.802%	$11.8531	$11.85	$11.85	$11.90
7 purchase totals =	$861.59		$930.8194	$930.82	$930.80	$930.80