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	$189.91	5.821%	$200.9647	$200.96	$200.95	$201.00
Purchase #2	$223.35	11.718%	$249.5222	$249.52	$249.50	$249.50
Purchase #3	$46.88	11.488%	$52.2656	$52.27	$52.25	$52.30
Purchase #4	$158.40	5.510%	$167.1278	$167.13	$167.15	$167.10
Purchase #5	$247.61	11.870%	$277.0013	$277.00	$277.00	$277.00
Purchase #6	$203.69	9.264%	$222.5598	$222.56	$222.55	$222.60
Purchase #7	$74.34	8.373%	$80.5645	$80.56	$80.55	$80.60
7 purchase totals =	$1,144.18		$1,250.0059	$1,250.00	$1,249.95	$1,250.10