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	$160.91	10.627%	$178.0099	$178.01	$178.00	$178.00
Purchase #2	$44.49	5.846%	$47.0909	$47.09	$47.10	$47.10
Purchase #3	$197.40	11.449%	$220.0003	$220.00	$220.00	$220.00
Purchase #4	$156.59	5.277%	$164.8533	$164.85	$164.85	$164.90
Purchase #5	$182.81	12.215%	$205.1402	$205.14	$205.15	$205.10
Purchase #6	$116.69	11.281%	$129.8538	$129.85	$129.85	$129.90
Purchase #7	$189.56	3.639%	$196.4581	$196.46	$196.45	$196.50
7 purchase totals =	$1,048.45		$1,141.4065	$1,141.40	$1,141.40	$1,141.50