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	$190.90	10.557%	$211.0533	$211.05	$211.05	$211.10
Purchase #2	$141.46	6.623%	$150.8289	$150.83	$150.85	$150.80
Purchase #3	$160.63	11.633%	$179.3161	$179.32	$179.30	$179.30
Purchase #4	$206.92	10.381%	$228.4004	$228.40	$228.40	$228.40
Purchase #5	$157.83	8.508%	$171.2582	$171.26	$171.25	$171.30
Purchase #6	$76.81	6.217%	$81.5853	$81.59	$81.60	$81.60
Purchase #7	$80.81	9.587%	$88.5573	$88.56	$88.55	$88.60
7 purchase totals =	$1,015.36		$1,110.9995	$1,111.01	$1,111.00	$1,111.10