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	$53.81	13.371%	$61.0049	$61.00	$61.00	$61.00
Purchase #2	$57.71	11.354%	$64.2624	$64.26	$64.25	$64.30
Purchase #3	$53.80	10.663%	$59.5367	$59.54	$59.55	$59.50
Purchase #4	$73.25	7.666%	$78.8653	$78.87	$78.85	$78.90
Purchase #5	$177.30	3.437%	$183.3938	$183.39	$183.40	$183.40
Purchase #6	$131.87	7.129%	$141.271	$141.27	$141.25	$141.30
Purchase #7	$153.68	12.238%	$172.4874	$172.49	$172.50	$172.50
7 purchase totals =	$701.42		$760.8215	$760.82	$760.80	$760.90