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	$152.98	9.684%	$167.7946	$167.79	$167.80	$167.80
Purchase #2	$228.55	8.862%	$248.8041	$248.80	$248.80	$248.80
Purchase #3	$166.83	7.679%	$179.6409	$179.64	$179.65	$179.60
Purchase #4	$225.89	7.509%	$242.8521	$242.85	$242.85	$242.90
Purchase #5	$16.86	6.134%	$17.8942	$17.89	$17.90	$17.90
Purchase #6	$67.25	11.417%	$74.9279	$74.93	$74.95	$74.90
Purchase #7	$66.55	8.626%	$72.2906	$72.29	$72.30	$72.30
7 purchase totals =	$924.91		$1,004.2044	$1,004.19	$1,004.25	$1,004.20