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	$211.61	10.787%	$234.4364	$234.44	$234.45	$234.40
Purchase #2	$233.44	4.718%	$244.4537	$244.45	$244.45	$244.50
Purchase #3	$52.25	3.873%	$54.2736	$54.27	$54.25	$54.30
Purchase #4	$85.76	11.737%	$95.8257	$95.83	$95.85	$95.80
Purchase #5	$198.58	6.283%	$211.0568	$211.06	$211.05	$211.10
Purchase #6	$231.33	12.240%	$259.6448	$259.64	$259.65	$259.60
Purchase #7	$27.84	12.609%	$31.3503	$31.35	$31.35	$31.40
7 purchase totals =	$1,040.81		$1,131.0413	$1,131.04	$1,131.05	$1,131.10