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	$143.80	9.234%	$157.0785	$157.08	$157.10	$157.10
Purchase #2	$38.53	7.724%	$41.5061	$41.51	$41.50	$41.50
Purchase #3	$143.72	6.655%	$153.2846	$153.28	$153.30	$153.30
Purchase #4	$132.32	4.542%	$138.33	$138.33	$138.35	$138.30
Purchase #5	$86.77	3.192%	$89.5397	$89.54	$89.55	$89.50
Purchase #6	$240.80	11.768%	$269.1373	$269.14	$269.15	$269.10
Purchase #7	$175.72	6.740%	$187.5635	$187.56	$187.55	$187.60
7 purchase totals =	$961.66		$1,036.4397	$1,036.44	$1,036.50	$1,036.40