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	$154.83	7.556%	$166.529	$166.53	$166.55	$166.50
Purchase #2	$66.87	11.546%	$74.5908	$74.59	$74.60	$74.60
Purchase #3	$172.55	9.270%	$188.5454	$188.55	$188.55	$188.50
Purchase #4	$204.52	13.826%	$232.7969	$232.80	$232.80	$232.80
Purchase #5	$87.95	3.172%	$90.7398	$90.74	$90.75	$90.70
Purchase #6	$84.33	6.683%	$89.9658	$89.97	$89.95	$90.00
Purchase #7	$142.50	11.797%	$159.3107	$159.31	$159.30	$159.30
7 purchase totals =	$913.55		$1,002.4784	$1,002.49	$1,002.50	$1,002.40