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	$245.34	8.268%	$265.6247	$265.62	$265.60	$265.60
Purchase #2	$157.63	5.810%	$166.7883	$166.79	$166.80	$166.80
Purchase #3	$233.27	3.139%	$240.5923	$240.59	$240.60	$240.60
Purchase #4	$6.97	3.677%	$7.2263	$7.23	$7.25	$7.20
Purchase #5	$167.26	8.294%	$181.1325	$181.13	$181.15	$181.10
Purchase #6	$105.66	9.558%	$115.759	$115.76	$115.75	$115.80
Purchase #7	$100.76	4.706%	$105.5018	$105.50	$105.50	$105.50
7 purchase totals =	$1,016.89		$1,082.6249	$1,082.62	$1,082.65	$1,082.60