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	$93.62	12.759%	$105.565	$105.57	$105.55	$105.60
Purchase #2	$69.42	13.527%	$78.8104	$78.81	$78.80	$78.80
Purchase #3	$219.93	12.789%	$248.0568	$248.06	$248.05	$248.10
Purchase #4	$90.83	8.308%	$98.3762	$98.38	$98.40	$98.40
Purchase #5	$240.98	13.524%	$273.5701	$273.57	$273.55	$273.60
Purchase #6	$80.81	3.142%	$83.3491	$83.35	$83.35	$83.30
Purchase #7	$56.40	7.809%	$60.8043	$60.80	$60.80	$60.80
7 purchase totals =	$851.99		$948.5319	$948.54	$948.50	$948.60