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	$199.82	3.559%	$206.9316	$206.93	$206.95	$206.90
Purchase #2	$75.98	13.345%	$86.1195	$86.12	$86.10	$86.10
Purchase #3	$142.39	4.381%	$148.6281	$148.63	$148.65	$148.60
Purchase #4	$90.59	13.604%	$102.9139	$102.91	$102.90	$102.90
Purchase #5	$183.40	9.197%	$200.2673	$200.27	$200.25	$200.30
Purchase #6	$35.29	11.842%	$39.469	$39.47	$39.45	$39.50
Purchase #7	$72.39	12.357%	$81.3352	$81.34	$81.35	$81.30
7 purchase totals =	$799.86		$865.6646	$865.67	$865.65	$865.60