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	$168.68	6.462%	$179.5801	$179.58	$179.60	$179.60
Purchase #2	$206.89	12.832%	$233.4381	$233.44	$233.45	$233.40
Purchase #3	$34.82	3.749%	$36.1254	$36.13	$36.15	$36.10
Purchase #4	$166.92	11.776%	$186.5765	$186.58	$186.60	$186.60
Purchase #5	$81.90	10.809%	$90.7526	$90.75	$90.75	$90.80
Purchase #6	$85.80	4.410%	$89.5838	$89.58	$89.60	$89.60
Purchase #7	$187.95	9.427%	$205.668	$205.67	$205.65	$205.70
7 purchase totals =	$932.96		$1,021.7245	$1,021.73	$1,021.80	$1,021.80