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	$58.59	5.569%	$61.8529	$61.85	$61.85	$61.90
Purchase #2	$244.90	5.110%	$257.4144	$257.41	$257.40	$257.40
Purchase #3	$35.30	8.861%	$38.4279	$38.43	$38.45	$38.40
Purchase #4	$233.45	7.507%	$250.9751	$250.98	$251.00	$251.00
Purchase #5	$69.80	3.852%	$72.4887	$72.49	$72.50	$72.50
Purchase #6	$108.30	5.515%	$114.2727	$114.27	$114.25	$114.30
Purchase #7	$154.44	5.446%	$162.8508	$162.85	$162.85	$162.90
7 purchase totals =	$904.78		$958.2825	$958.28	$958.30	$958.40