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	$239.53	4.179%	$249.54	$249.54	$249.55	$249.50
Purchase #2	$78.47	4.682%	$82.144	$82.14	$82.15	$82.10
Purchase #3	$38.96	11.583%	$43.4727	$43.47	$43.45	$43.50
Purchase #4	$97.77	3.113%	$100.8136	$100.81	$100.80	$100.80
Purchase #5	$142.25	3.871%	$147.7565	$147.76	$147.75	$147.80
Purchase #6	$69.88	10.692%	$77.3516	$77.35	$77.35	$77.40
Purchase #7	$97.74	7.356%	$104.9298	$104.93	$104.95	$104.90
7 purchase totals =	$764.60		$806.0082	$806.00	$806.00	$806.00