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	$206.67	5.800%	$218.6569	$218.66	$218.65	$218.70
Purchase #2	$245.75	5.755%	$259.8929	$259.89	$259.90	$259.90
Purchase #3	$61.65	5.471%	$65.0229	$65.02	$65.00	$65.00
Purchase #4	$163.93	5.147%	$172.3675	$172.37	$172.35	$172.40
Purchase #5	$159.69	3.812%	$165.7774	$165.78	$165.80	$165.80
Purchase #6	$152.25	10.402%	$168.087	$168.09	$168.10	$168.10
Purchase #7	$234.63	5.839%	$248.33	$248.33	$248.35	$248.30
7 purchase totals =	$1,224.57		$1,298.1346	$1,298.14	$1,298.15	$1,298.20