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	$220.40	7.468%	$236.8595	$236.86	$236.85	$236.90
Purchase #2	$176.55	11.445%	$196.7561	$196.76	$196.75	$196.80
Purchase #3	$93.82	10.372%	$103.551	$103.55	$103.55	$103.60
Purchase #4	$91.94	5.136%	$96.662	$96.66	$96.65	$96.70
Purchase #5	$214.61	9.814%	$235.6718	$235.67	$235.65	$235.70
Purchase #6	$42.36	7.611%	$45.584	$45.58	$45.60	$45.60
Purchase #7	$36.74	4.700%	$38.4668	$38.47	$38.45	$38.50
7 purchase totals =	$876.42		$953.5512	$953.55	$953.50	$953.80