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	$163.74	10.501%	$180.9343	$180.93	$180.95	$180.90
Purchase #2	$138.38	6.872%	$147.8895	$147.89	$147.90	$147.90
Purchase #3	$156.64	9.515%	$171.5443	$171.54	$171.55	$171.50
Purchase #4	$79.76	3.784%	$82.7781	$82.78	$82.80	$82.80
Purchase #5	$166.50	3.601%	$172.4957	$172.50	$172.50	$172.50
Purchase #6	$124.55	6.540%	$132.6956	$132.70	$132.70	$132.70
Purchase #7	$129.87	10.190%	$143.1038	$143.10	$143.10	$143.10
7 purchase totals =	$959.44		$1,031.4413	$1,031.44	$1,031.50	$1,031.40