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	$243.96	11.173%	$271.2177	$271.22	$271.20	$271.20
Purchase #2	$51.64	3.804%	$53.6044	$53.60	$53.60	$53.60
Purchase #3	$76.33	8.183%	$82.5761	$82.58	$82.60	$82.60
Purchase #4	$211.65	12.658%	$238.4407	$238.44	$238.45	$238.40
Purchase #5	$167.52	6.658%	$178.6735	$178.67	$178.65	$178.70
Purchase #6	$149.77	12.525%	$168.5287	$168.53	$168.55	$168.50
Purchase #7	$179.68	13.302%	$203.581	$203.58	$203.60	$203.60
7 purchase totals =	$1,080.55		$1,196.6221	$1,196.62	$1,196.65	$1,196.60