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	10.820%	$186.9312	$186.93	$186.95	$186.90
Purchase #2	$82.54	3.662%	$85.5626	$85.56	$85.55	$85.60
Purchase #3	$96.37	12.259%	$108.184	$108.18	$108.20	$108.20
Purchase #4	$171.26	11.334%	$190.6706	$190.67	$190.65	$190.70
Purchase #5	$82.30	11.610%	$91.855	$91.86	$91.85	$91.90
Purchase #6	$100.41	13.384%	$113.8489	$113.85	$113.85	$113.80
Purchase #7	$141.72	4.749%	$148.4503	$148.45	$148.45	$148.50
7 purchase totals =	$843.28		$925.5026	$925.50	$925.50	$925.60