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	$102.86	9.158%	$112.2799	$112.28	$112.30	$112.30
Purchase #2	$28.77	10.318%	$31.7385	$31.74	$31.75	$31.70
Purchase #3	$63.68	6.692%	$67.9415	$67.94	$67.95	$67.90
Purchase #4	$102.59	8.555%	$111.3666	$111.37	$111.35	$111.40
Purchase #5	$154.55	13.557%	$175.5023	$175.50	$175.50	$175.50
Purchase #6	$42.65	9.856%	$46.8536	$46.85	$46.85	$46.90
Purchase #7	$225.42	4.497%	$235.5571	$235.56	$235.55	$235.60
7 purchase totals =	$720.52		$781.2395	$781.24	$781.25	$781.30