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	$140.59	5.628%	$148.5024	$148.50	$148.50	$148.50
Purchase #2	$82.83	11.719%	$92.5368	$92.54	$92.55	$92.50
Purchase #3	$186.64	12.763%	$210.4609	$210.46	$210.45	$210.50
Purchase #4	$82.26	4.209%	$85.7223	$85.72	$85.70	$85.70
Purchase #5	$90.76	10.783%	$100.5467	$100.55	$100.55	$100.50
Purchase #6	$26.93	3.539%	$27.8831	$27.88	$27.90	$27.90
Purchase #7	$243.80	6.392%	$259.3837	$259.38	$259.40	$259.40
7 purchase totals =	$853.81		$925.0359	$925.03	$925.05	$925.00