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	$208.32	5.420%	$219.6109	$219.61	$219.60	$219.60
Purchase #2	$104.71	10.289%	$115.4836	$115.48	$115.50	$115.50
Purchase #3	$156.52	5.128%	$164.5463	$164.55	$164.55	$164.50
Purchase #4	$151.61	9.119%	$165.4353	$165.44	$165.45	$165.40
Purchase #5	$189.60	9.102%	$206.8574	$206.86	$206.85	$206.90
Purchase #6	$205.57	8.124%	$222.2705	$222.27	$222.25	$222.30
Purchase #7	$32.91	13.418%	$37.3259	$37.33	$37.35	$37.30
7 purchase totals =	$1,049.24		$1,131.5299	$1,131.54	$1,131.55	$1,131.50