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	$54.25	13.693%	$61.6785	$61.68	$61.70	$61.70
Purchase #2	$203.87	7.169%	$218.4854	$218.49	$218.50	$218.50
Purchase #3	$168.41	13.336%	$190.8692	$190.87	$190.85	$190.90
Purchase #4	$77.59	3.432%	$80.2529	$80.25	$80.25	$80.30
Purchase #5	$94.87	6.280%	$100.8278	$100.83	$100.85	$100.80
Purchase #6	$241.65	13.282%	$273.746	$273.75	$273.75	$273.70
Purchase #7	$248.52	4.112%	$258.7391	$258.74	$258.75	$258.70
7 purchase totals =	$1,089.16		$1,184.5989	$1,184.61	$1,184.65	$1,184.60