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	$248.61	9.598%	$272.4716	$272.47	$272.45	$272.50
Purchase #2	$75.93	3.259%	$78.4046	$78.40	$78.40	$78.40
Purchase #3	$92.70	8.689%	$100.7547	$100.75	$100.75	$100.80
Purchase #4	$217.97	13.842%	$248.1414	$248.14	$248.15	$248.10
Purchase #5	$54.72	7.544%	$58.8481	$58.85	$58.85	$58.80
Purchase #6	$87.54	4.439%	$91.4259	$91.43	$91.45	$91.40
Purchase #7	$182.88	9.353%	$199.9848	$199.98	$200.00	$200.00
7 purchase totals =	$960.35		$1,050.0311	$1,050.02	$1,050.05	$1,050.00