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	$213.30	10.337%	$235.3488	$235.35	$235.35	$235.30
Purchase #2	$95.44	4.816%	$100.0364	$100.04	$100.05	$100.00
Purchase #3	$140.54	11.342%	$156.48	$156.48	$156.50	$156.50
Purchase #4	$123.35	11.494%	$137.5278	$137.53	$137.55	$137.50
Purchase #5	$143.41	4.688%	$150.1331	$150.13	$150.15	$150.10
Purchase #6	$83.36	7.713%	$89.7896	$89.79	$89.80	$89.80
Purchase #7	$237.32	9.837%	$260.6652	$260.67	$260.65	$260.70
7 purchase totals =	$1,036.72		$1,129.9809	$1,129.99	$1,130.05	$1,129.90