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	$176.90	3.508%	$183.1057	$183.11	$183.10	$183.10
Purchase #2	$98.41	13.430%	$111.6265	$111.63	$111.65	$111.60
Purchase #3	$83.72	11.871%	$93.6584	$93.66	$93.65	$93.70
Purchase #4	$108.89	3.450%	$112.6467	$112.65	$112.65	$112.60
Purchase #5	$9.96	6.308%	$10.5883	$10.59	$10.60	$10.60
Purchase #6	$225.27	11.675%	$251.5703	$251.57	$251.55	$251.60
Purchase #7	$68.61	10.853%	$76.0562	$76.06	$76.05	$76.10
7 purchase totals =	$771.76		$839.2521	$839.27	$839.25	$839.30