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	$162.49	6.181%	$172.5335	$172.53	$172.55	$172.50
Purchase #2	$86.56	4.623%	$90.5617	$90.56	$90.55	$90.60
Purchase #3	$124.48	6.340%	$132.372	$132.37	$132.35	$132.40
Purchase #4	$33.93	11.396%	$37.7967	$37.80	$37.80	$37.80
Purchase #5	$46.25	10.481%	$51.0975	$51.10	$51.10	$51.10
Purchase #6	$98.86	9.271%	$108.0253	$108.03	$108.05	$108.00
Purchase #7	$93.71	3.253%	$96.7584	$96.76	$96.75	$96.80
7 purchase totals =	$646.28		$689.1451	$689.15	$689.15	$689.20