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	$89.54	7.869%	$96.5859	$96.59	$96.60	$96.60
Purchase #2	$106.27	7.779%	$114.5367	$114.54	$114.55	$114.50
Purchase #3	$59.67	13.665%	$67.8239	$67.82	$67.80	$67.80
Purchase #4	$242.72	12.616%	$273.3416	$273.34	$273.35	$273.30
Purchase #5	$25.92	3.570%	$26.8453	$26.85	$26.85	$26.80
Purchase #6	$176.81	12.605%	$199.0969	$199.10	$199.10	$199.10
Purchase #7	$108.25	7.526%	$116.3969	$116.40	$116.40	$116.40
7 purchase totals =	$809.18		$894.6272	$894.64	$894.65	$894.50